Low-key keyboards are a fad
When I realized that I needed a split ergonomic mechanical keyboard, I dove deep into the space, searching for something that could work for me. I quickly found the ZSA family of keyboards, but they were completely outside my budget. I also ran into the Kinesis Advantage and Advantage360, but not only were they also completely outside my budget, I also didn't like the straight up and down wrist angle of the Advantage, and the thick, tall design of the 360, nor the thumb cluster design that looked awkward to reach, and I didn't want to lock myself into proprietary firmware for programming the keyboard either, since I had wonderfully baroque ideas for what I wanted to do.
As my search deepened, I soon found myself immersed in the world of DIY ergonomic split keyboards. Generally, the ideas and design principles of this space were good, centered around rectifying very real and pertinent design flaws in traditional keyboards through such things as splitting, tenting, column-staggered key layouts, splayed key columns, low-profile housings, and mechanical key switches.
The space was not free from its share of blind trend-following and folk wisdom, however. One of the most baffling examples of this was the single-minded focus of the whole community at large on something which I can only call keyboard minimalism: the endless desire to seek the absolute minimum number of keys they could get away with on their keyboard designs, and the general dismissal of designs with more keys through the assumption that everyone, eventually, would ultimately move toward keyboards with a smaller number of keys over time, as those were just obviously superior.
You can see this thinking in the fact that nearly every relatively mainstream, well-known, often-recommended DIY split ergonomic keyboard design has very few keys. While a standard keyboard has anywhere from 90 to 104 keys, the average DIY split ergomech keyboard, like the popular accessible starter the Keebio Iris, or the even more popular and highly regarded Sofle design – which in turn was designed based on popular designs with similar key counts like the Lily58 and Helix – seems to have half that, around 58 keys, at a maximum. Many go even lower, too – the very popular and widely regarded as "endgame" (i.e. perfect, if you can adapt to it) Corne keyboard only has 42.
I even spent some time on Compare Split Keyboard looking for a design with enough keys for me – someone who prefers roughly the number of keys and keyboard size of a tenkeyless – and was shocked to find that the orthodox dogma in this community that fewer keys = better was so complete that, out of all of the many hundreds of varied split ergonomic mechanical keyboard designs that list documented, not a one had more than 80 keys. It seemed no one even thought to want this, let alone sit down and design it. Questions on related forums asking about keyboards with more than a mere handful of keys are met with usually one, maybe two, actual options, a suggestion or three to design your own keyboard, and several people simply telling the questioner that they're wrong for wanting more than about 60 keys or fewer.
Apparently it's become received wisdom in these niche circles that using keyboard layers – where you tap or hold a special modifier button that changes the meanings of some or all of the keys on your keyboard, to emulate having more keys – to make up for missing navigation clusters, symbol keys, function keys, modifier keys, and often even number keys, is superior to simply having enough keys on your keyboard for all the basic things you need to do. The argument for this tends to be simple: for the sake of efficiency and minimizing effort/strain, why reach an extra row or column or two for a key, when you could instead hold down a key that's readily available under one of your fingers (perhaps the thumb or index finger) and have the key you want appear under you?
There are several problems with this logic. First of all, there's the problem of how to activate your layers: do you want to toggle the layer on and off with a key tap, in which case you have to remember what layer you're on, since most keyboards don't have a screen or way to communicate with the computer to display what layer you're on, unlike modal editors? Or do you want to treat layers as an additional modifier key, in which case you run into the problem of key arpeggios versus key chords, that being that key chords are inherently difficult and unergonomic? (Doubly so with keys that need to be modified in some other way, such as with the control or shift key, while also being activated by a layer). Moreover, with every layer you add, you're introducing more complexity to keep in mind. Control, Meta, Shift, and Super all introduce their own layers, and now you want to introduce one or two (sometimes up to six) additional layers into the mix that you have to have memorized?
More than that, the number of layers you'll need to use is going to scale with the smallness of your keyboard, but as the number of layers you want to access increases, so too does the number of keys needed to actually access those layers, meaning that as the number of available keys on your keyboard gets more and more cramped, the number of keys that have to be occupied with layer-switching increases. You can try to mitigate this via having keys do different things when you tap on them versus when you hold them, so that they can do double-duty, but now that's just more that you have to remember, and, depending on what keys you choose, inconsistent semantics between keys that repeat when held and keys that activate a layer when held, which, combined with layers changing the meaning of possibly all the other keys on your keyboard, is a recipe for turning your keyboard into a fucking minesweeper game.
More problematic than any of this, though, is the fact that by using layers to regain missing number, symbol, and navigation keys, in addition to the letter keys on the base layer that you have just enough room for, you're essentially converting entering different types of input into entirely separate modes, like on a mobile keyboard, instead of things that you can fluidly move back and forth between. In order to enter something like $variable4, you've now got to switch to your symbol layer for a single symbol, then back to your base layer for the main word, then to your number layer, and then back again so you can type space after it, and good luck typing something like mathematics.
Can this be overcome? Sure, and clearly many people do. But the point I'm making here is that juggling layers isn't cost-free. There's a huge learning curve and a lot of inherent cognitive overhead that is unlikely to be something you can easily encode into muscle memory and not have to worry about anymore, and there are a lot of inherent points of friction even if you do manage to actually turn all this detail into muscle memory.
This has the knock-on effect that you're going to want to try to cram all of your most used keys and symbols onto your base layer, which is a recipe for endless tinkering and adjustment trying to find the optimal layout for your keyboard, tetrising everything into the most awkward and inconsistent positions in an attempt to shove it all in there.
And all for what? Is having to move your finger one less row or column really a big gain compared to having to press (or especially hold) one extra key and keep all the rest of this stuff in your head while you do? In extreme cases, this might be the case (imagine a keyboard with no shift key, just duplicated keys for everything), but in my opinion the advantages of layering only hold when the alternative is often-used keys being shoved out of easy reach of your fingers without having to move your hands. In a situation where all the keys in question are within reach of your fingers anyway, saving your fingers some distance of movement just to add an extra key to hit or extra chord to hold down doesn't seem like a clear win to me.
Just take it from my girlfriend, who initially dismissed my strongly voiced concerns with her purchase of a $160 Keyboardio Atreus (which has only 44 keys), but who – as I'm writing this – I just found out has completely given up on learning to use the keyboard for precisely the reasons above:
The longer I used it, and the more different things I used it for, the more unavoidable the fact was that the limited number of keys was hampering my productivity, primarily due to the necessity to switch back and forth between different layers. My primary beef was with the lack of accessible number keys, which made navigation in my window manager difficult, made inputs that were mixed difficult, and overall the necessity in a lot of the software I used to switch between typing and numbers and game style WASD input makes the limited key set an absolute pain to use. It was bad enough that I came to feel anxious when I was going to have to use the keyboard, and found respite in my T420 laptop keyboard instead. Furthermore, the small number of keys makes placing symbols in quickly memorable positions impossible. So you wind up having to learn a lot more.
Why not avoid bringing all this trouble down on your head by just using a keyboard that has enough keys to put all the letters, symbols, numbers, and navigation keys you need right at your fingertips? I suspect the real answer isn't actually the ergonomic benefits, but the allure of small size, minimalism, and trying to be different. I hope, in a few years, this trend dies down and we see more approaches like that of the Glove80.
As a final parting shot, it behooves me to point out the fact that a keyboard with more keys can always emulate a keyboard with less keys – simply design a layer system according to your preferences for the larger keyboard, and then ignore all the keys outside the range you're willing to reach – with much more customizability because you can decide how far you want to reach on an individual, case by case basis if you like, since there's actually more keys to extend to, whereas a smaller keyboard can't emulate a larger one. As long as you're not desperately hurting for desk space, or thinking about getting a Space Cadet keyboard or a Hyper7, then, it's always more sensible to get a larger keyboard even if you're not convinced by the arguments above.