The world of Den is, presumably, a very hot place where too many clothes can be stifling. The people don’t actually sweat, though – they glisten. But they sure do spend a lot of time naked. To Corben’s credit, he does show full frontal male nudity in panel one – to balance out the topless queen lounging around on the rest of the page, I guess? 

(Heavy Metal issue #69, December 1982 – Page 40 Den II by Corben)