Even with the military ones you have a regulation shirt you wear under it. That is the one you change. You will still wear the same jacket and pants everyday. I think I might have had two pair of pants... By year three, things can get pretty ratty.
You can keep them, but by the time you have spent all day every day in the same outfit, most people get rid of them. They don't have to give them back. No one would wear a dirty, old, hand me down uniform anyway.