It’s more practical to have definition in that area and it can’t be achieved otherwise
People have often made fun of Superman (and other superheroes) for wearing undies over his costume but his day to be avenged has finally come. Thanks to a Quora user, we have an answer for this out of the ordinary fashion trend.As it turns out, because superheroes are meant to be, you know, super, certain male or female traits or areas were emphasized from the get go in the comics, mostly because the panels were small and the quality of the print left a lot to be desired.
In Superman’s case, those wore the groin and the chest.
Then, there was a practical consideration at play, as Quora user Ariel Williams points out: if the red undies were not there, Superman would look like his leg and his groin would be one and the same.
Williams even includes a drawing of Superman with and without the undies, with the obvious conclusion being here that the no-undies Superman isn’t really that super.
“Even characters that wore only a single color often had detail lines outlining the pelvis from the rest of the body so their features could easily be made out on small panels,” Williams says.
However, “modern comics are starting to move away from this trend a little as better printing technology has allowed smooth gradients and shading to compensate for the issues of the past and opened up a whole new range of possibilities,” she adds.
So there, now you know why Superman never wears his underwear underneath his costume, at least in the comics.