What's with the mole under the eye?

[humon]

So many anime images and video game characters I've seen have a mole under one eye or the other. It's so frequent that it can't just be random. What's the deal with that? Is there like a selfish-gene kind of explanation, where guys with that mole subconsciously seek out women who also have that mole as a sign they are genetically compatible? To me, all moles are ugly, and all of these characters would have been much more attractive with a clear face. So I don't understand why an artist would add one.