No Shirt, No Shoes....

Why do guys take their shoes off while they are in class or at school? Today I have observed this phenomena three times & I just don't understand it. I have observed it on other days. It is winter so I am guessing their feet can't be hot. Guys wear loafers or tennis shoes, so I find it hard to believe that they find their shoes so uncomfortable or something to keep them on their feet. I wear 4 1/2 heels all day long and don't take my shoes off. My shoes are not particularly comfortable, but I manage to keep my feet covered when in public. I don't get why guys don't find footwear in public places to be necessary. Can anyone explain this to me?