Not exactly something I had ever thought about, but io9 has an interesting post about how comic book characters came to have their underwear on the outside and why the industry shouldn’t bail on the innovation now. The money quote:
Underpants on tights were signifiers of extra-masculine strength and endurance in 1938. The cape, showman-like boots, belt and skintight spandex were all derived from circus outfits and helped to emphasize the performative, even freak-show-esque, aspect of Superman’s adventures. Lifting bridges, stopping trains with his bare hands, wrestling elephants: these were superstrongman feats that benefited from the carnival flair implied by skintight spandex. [Artist Joe] Shuster had dressed the first superhero as his culture’s most prominent exemplar of the strongman ideal, unwittingly setting him up as the butt of ten thousand jokes.