You can buy ZSA split keyboards with labels on the keycaps. Its great while you are still learning to type on these rather exotic keyboards. As you get more proficient, you start to rely more and more on the "central" keys (using layers toggles to put, say arrow keys on the home row). Muscle-memory is often more than enough.

That said, I have kept the number row labelled. These keys are not obscured by your hands and they can give you the necessary frame of reference. The ideal trade-off for me.