Max Landis is writing a unique perspective on Superman's story within the pages of SUPERMAN: American Alien, and he has released a sneak peak into some dialogue that answers the question:

"What's the deal with Superman's red underwear?"

Okay, so it's not underwear. But it is a required garment when you consider the skin-tight nature of the blue suit...

While the "New52" abolished the spandex in favor of Kryptonian armor, thereby eliminating the need for the red shorts, it's clear that if the Man of Steel ever went back to fabric, adding an extra layer isn't a bad idea.