if you want to use blank keycaps for aesthetic purposes, the assumption is that you are a touch typist and know what all the keys are without looking at the legend. For people that use unusual layouts, such as ergodox or ortholinear layouts, a large part of transitioning to that is learning the keyboard properly, which blanks kind of force you to do. That, and for certain layouts the key profiles will not match up properly (trying swapping your number 1 and Z keys and see how awful it is).