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.
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.