I have a feeling when it comes to contemporary superhero costumes, there’s the aim of making them look more like military uniforms. Actually some army and police uniforms already do put on armour, this makes such sentiments and designs not much of a stretch. Especially when it comes to protection and the odd fact that most superhero costumes look terrible in the flesh.
If I’m not mistaken, somebody said that wrestling costumes do resemble superhero costumes but do blur the line between what’s sexualised and what’s practical. It’s pretty much up to the individual wrestler if they want to show skin or not but still have to be protective enough to avoid mishaps in combat. In fact those wrestling outfits are actually fought in.
Not to mention, unless if it’s in places that permit more modest clothing, they need to be breathable and allow the fighter to cool down. The wrestling costumes are good but I suspect the armour like outfits in superhero films have the pretension of belonging to government bodies (like armies and police) that it won out in superhero media.