I witnessed a supervisor putting on a belt and tucking in their shirt. I must have given a funny look because they said, "I'm just getting dressed again after a drill." I laughed and asked why it involved getting undressed and they said that they regularly do drills where supervisors go through in plain clothes. I didn't ask anything further about it, but it did strike me as pointless. Just because the supervisor is in plain clothes that doesn't mean all the people they supervise won't recognize them by their face.