It’s about hand movement, not desk space.

The “missing” keys are on additional layers reached via a modifier key, or by overloading keys on tap/hold, or by increasingly esoteric methods the smaller the board gets: chording, tap dance, etc. They’re typically no less accessible than capital letters, while allowing you to keep your fingers on the home row.

For me, the additional keys on my larger keyboards rarely prove useful in practice. I end up mostly using the same subset available on the 60% I’m typing on now – it’s quicker and more comfortable than reaching over to the dedicated key.