The first reply is correct. You are talking about the membership behavior and not the uniform. Band and corps uniforms are the same. How members treat them MAY be different.
Although, I have seen many many bands here in Texas, including every one I've ever worked with, have a great deal of discipline when it comes to uniforms. There will always be children (I emphasis that word) that think "Eff this I'm in band for the credit and I'll walk around with my uniform unzipped", but those students always meet consequences (again, speaking from personal experience, not saying all programs do this.)
Example: The LD Bell Marching Band gets is very professional in uniform. Those kids know that if they don't that the director and even their peers will come down on them. They sit in an organized block in the stands while waiting for score announcements. No moving, no talking, and no cheering for yourself when they announce you've won. Much like many DCs do in retreat.
Many marching bands have the same respect because their directors are FMMs of corps from all over the country from all different eras. It would make sense that that tradition of uniform respect trickle down.
In short, don't paint with such a broad brush.