Why?

I can wear a pair of 4-inch heels all day every day without incident. I can walk fast, run, carry heavy boxes and bags (no, not my purse) and given the opportunity, I’m sure I could climb Mount Everest in heels. (I might lose a toe to frostbite, though). So why can’t I take two steps in my bare feet without jamming my toe or slamming my knee into a corner?