Being a superhero is about as manly as it gets. They're strong, smart, independent, and they save people! You know what else is manly? Beards. Mustaches too.
So why is it the two so rarely coincide? Why are there so many superheroes with tons of hair but no facial scruff? What's with all the baby-faced heroes running around? Bearded superheroes just kick ass. Logically, a beard would be a pretty big giveaway to your secret identity if you don't wear a full face mask. Imagine Bruce Wayne trying to convince people he wasn't Batman but as they both started rocking the exact same Batbeard or Batstache at the exact same time? Also, beards must be really itchy under a Spider-Man-style mask. You'll notice most of the characters on this least either don't have a superhero secret identity, or they're villains, so they don't need one.
There's also the fact that beards are much much harder to draw and be consistent with than a clean shaven jaw. But that's neither here nor there.
A few of these heroes don't always rock the facial haired look seen on this list of comic book characters with facial hair, but in those cases, the 'staches and beards are so badass they speak for themselves.