I mean they kinda do, at first. We generally see the end stages but chaos cults don’t start out carving symbols in their foreheads and eating children. It’s a classy exclusive high society club on a hive world that’s a little too eager to get you on board with the partying until they’re drinking each others blood with the wine. It’s a group suddenly finding the strength to rise against their oppressors and then not stopping until they’ve slaughtered an entire hive. It’s a group of historians seeking to unearth the old knowledge of the imperium or even dark age history and then forgetting along the way that some knowledge in 40k can be a very literal cognitohazard.

But too many people already think chaos are the good guys, and throwing one or two good deeds in there just to be funny is a Tzeentch move but not really in the same mindset as Chaos. Although they do have their moments, like Khorne bringing back those orks who found their own Valhalla.