Head surgeon sees medical student running around at a local restaurant in green scrubs and is totally incensed that someone would "steal" scrubs from his hospital.
He returns to work and tells everyone about the "stolen" scrubs he saw everywhere (We have a anti-stealing scrub device that checks out scrubs to each person by their ID badge)
Decides to forbid all scrubs outside the hospital due to possible infection spread and how would it look to outsiders who get surgery and have seen the scrubs in the outside dirty world (they are mostly unconscious or can't remember who they saw, let alone what they were wearing)
So another dumb rule. Particularly when you see surgeons wearing their horse dung covered boots with no covers into the OR for surgery. It's shocking how retarded this system can be sometimes.