Yes, the design intent of coordinated audio/visual moments is worth noting. But unlike film, the music and visual aspects of drum corps are also judged separately, every time they are performed live in a contest. Designers write with those judges in mind. They are incentivized to create a product that, while coordinated motion to music, also appeals to people who focus on one aspect to the relative exclusion of the other. And as a result, they still do - at least in my opinion, the musical programs are just as viable a standalone product as they were in 1990, 1980, 1970, 1960, etc.
We all enjoy drum corps in our own ways. For me, while I appreciate A/V coordination, I do not need to see it repeatedly on a video recording. But I do need to hear that music, again and again. So I get my drum corps fix from CDs (or better yet, APDs in recent DCI years).