Viltrum’s Facial Hair Game

Apologies in advance if this has been asked to death or if this is the wrong place to be posting.

Speaking as someone who has never read the comics and only seen the show, I recently saw a piece of art with a whole mess of different Viltrumites from the comics, and all of the men had moustaches. Can anyone explain to me why? Is that just how they look? Is it a cultural thing? Some kind of wild alien physiology? Will we get a moustachioed Mark eventually?