My feet are gross. They often sweat a lot. My socks are often damp after a 10 hour day at work. If I were to try wearing them the next day without washing them, they would be all crusty (not to mention smelly). I would be totally miserable.

I sometimes wear jeans more than once without washing them. Only if they didn't get visibly dirty though. I don't feel gross doing that. I would feel gross wearing a t-shirt, underwear, or socks twice though.