Just because things are "the way we've always done them" doesn't mean there's a good reason for that.

I'm willing to bet that the origin of "percussion always stands" was from old school directors who spent the entire rehearsal on their fortress podium and never once moved around the room.

Virtually no one does that anymore - we're much more aware of the value of proximity. We move around the ensemble pretty consistently - and if you aren't, as a director, you're doing your students a disservice. You'll hear things next to the horns that you wouldn't hear from the podium.

Orchestras - as several video examples show in this thread - don't follow this. Professional and collegiate bands don't follow this.

If one is always having discipline problems with the percussion section, the problem isn't with the kids - it's with the teacher.