I won't require high-ranking female members of my organization to wear a stainless-steel bustier. Morale is better with a more casual dress-code. Similarly, outfits made entirely from black leather will be reserved for formal occasions.
Evil quite often has a different style compared to heroes and bystanders. Perhaps it's a way to tell the heroes and villains apart, perhaps it's because the artists and costumers think Evil Is Cool
, or perhaps a little bit of all of them.
Regardless, these tropes involve fashion choices villains make (intentionally or otherwise).
Also, some of the more extreme Anti Heroes
are likely to follow these tropes.
Compare Hollywood Dress Code