Undoubtedly, programmers are a major user of keyboards, and IDE developers love function keys for esoteric shortcuts for debugging, moving around, and running code. So why do so many split keyboards not actually have the function keys.
I think makers are missing out a huge audience.
Probably because layering and chording easily let you access the F-keys while not having them take up so much space.
But some f key shorcuts already need ctrl + alt/shift pressing so you don’t have many options for switching to a different layer.
My shift and layer switch are both under my thumb so I can hit cmd+ opt/ctrl + shift + layer shift and an F key all at once with only 4 fingers.
I use Extend by Dreymar which includes the alt, shift, and even control keys. This lets me almost exclusively use the homerow for key binds, which is great if you’re on a laptop keyboard or similar.