While I'd like to believe these people think, "If I can't be beautiful, no one can!" I think it's more likely that their sense of what's appealing and what's not is broken beyond repair.
They're trying to make the unappealing appealing, and that's why this art feels so wrong. Unappealing features can be easy to look at
if you know they're unappealing. Look at the art of Basil Wolverton, for example:
Ugly? Sure. But does it feel wrong like some of the art posted in this thread? No, because Wolverton knew that he was trying to draw something ugly and didn't try to make it appealing. These people believe they can get you to like ugly features, and that's why they fail at art.