Why do we get scruffy heels when we wear sandals?

Question

Why do we get scruffy heels when we wear sandals?

Answer 1

If you mean a callus, it's a natural response to pressure and friction.  Your body was designed for walking barefoot.  When you do so, the skin contacting the ground adapts to the increased wear.  The foot is working as designed.

Answer 2

Because of friction.  It is the same concept of getting a calis on your hand, or a constructions workers rough hands versus a busnismans hand.  Your heal  has increase friction because the heal of the sandal is not held tight to your foot so the friction makes you skin tough.