My entire family used to go barefoot all summer. By August, the soles of our feet would be the consistency of hard plastic and could walk comfortably over hot asphalt, gravel, and even small slivers of broken glass. Over the winter the callus would peel off in sheets, leaving our feet soft and supple again.
These days I’m diabetic and live with reduced circulation and peripheral neuropathy in my feet, so an infection can mean gangrene, amputation, and even death. I wouldn’t worry if my feet were already toughened, but getting to that state is probably too risky. Also, even tough callus is unlikely to protect you from your entire weight pressing unto a rusty nail, so old barns would be a no-go in any case.