There are only a few competitive or recreational summer activities where the players are traditionally clad head to toe, wrist to ankle. NASCAR, reenactments, and drum corps. In NASCAR, it's for safety; in reenactments it's for authenticity, and in DCI it's... well, we've always done it this way.
Both reenactments and drum corps owe the genesis to their military roots, and in drum corps, it's more closely tied to present-day marching bands. But despite the temperature difference, the summer activity has historically parted relatively little from their colder weather counterparts. This year may represent the largest departure from traditional uniforms, with short sleeves, no sleeves, and a variety of lighter weight materials being represented on the field. I'm certain current marching members think it's about time, and former marching members add another notch to their "back in my day..." belt. And, of course, it's probably no small coincidence that the Bluecoats just won a championship with nontraditional uniforms.
While I air musically on the traditional side, I mostly welcome this potential renaissance in uniform design. While I prefer corps pick a style and stick to it -uniformity across time, if you will - I've got no problem with them picking styles, lengths, and fabrics that will make the marching members' experience a little more pleasant.