It always weirded me out how wearing underwear as outerwear look became the staple fit for superheroes. Like I understand you gotta look different from civilians but wearing an underwear on the outside? A cape wasn't enough?
It was the circus strongman look, and due to being unusual and exotic compared to the actual outfits people wore it even seemed to take over as a general futuristic look for a while.
To elaborate on this:
Circus strongmen wore spandex bodysuits because the material would show off every muscle in their body.
Do you know what else it would show off?
That's why they wore trunks over their spandex.