Hardness is compression and it's very difficult to tear things by compressing them....you'd have much bigger problems if your more concerned with hardness than friction when taking about tearing feet and hands...think squished hotdogs and how they tear.

Like have you never walked across a rocky stream barefoot? Ever think about the guys who stand barefoot for hours in the water fishing? Seems like they'd be losing feet, left and right, lol.

Hardness has little to do with it, things like trench foot are created by friction not compression and even then trench foot takes a very long time to occur if you're barefoot, because reduced friction..