If you're playing drums in a marching band you're likely playing outside, and fighting to be heard above brass players, so you'll need as much volume as you can get.
As with most bass gear, damping improves the tone of a drum kit in a rock environment. You don't want the note to ring on and interfere with the other notes being played, you want it to punch through and then die. You don't see many beer mats gaffered to skins these days but they performed the same function. I love Micky Waller's sound.
I play with a couple of drummers using Jazz type setups on their kits. With their "polite" and toppy sound they don't sound half as good as the regular rock guys.