I have always put it down to "Do As I Say, Not As I Do" syndrome.
It's probably not so bad as long as they change footwear.
Mind you, in some places I have been (overseas), the biomeds have been the most prolific "offenders" (mea culpa
But the nice thing about wearing theatre clothes all day (week) is that you can simply bung them into the hospital laundry and draw out a fresh set. You know it makes sense. An added plus:- no ties in the theatres.