Back when I had to pass proficiency on my bass, I practiced for something like five hours a day, and most of the pads on my left hand became completely smooth callouses. Which was funny because to get my driver's license updated I had to provide prints and they didn't match, even my thumb had a callous on the side from playing in thumb position so it blanked out the whole left side of my print.
They had to verify with the right hand, but from playing electric bass at the same time only two fingers looked the same.
Stupid society not adjusting for artist lifestyles.