No one smart and beautiful

As I was browsing the TV Tropes wiki, I suddenly got an idea. Maybe there's a perfectly good reason why nerds are stereotypically portrayed as ugly, socially inept, or crazy eccentric.

It could be because nerds in fact do display these qualities, and the stereotypes merely exaggerate them. But we don't like that answer, 'cause that would have negative implications about ourselves. Cognitive dissonance!

But anyways, in my sudden moment of what might be called "inspiration" by excessively optimistic folks on a good day, I had a different idea. There are few perfectly smart, well-adjusted, attractive individuals in fiction because that would fall into the Mary Sue archetype. The Mary Sue is a character that has everything going for her in unrealistic quantities. Everything in the story centers around Mary Sue, and the conflicts only exist so that she can overcome them. Though the Mary Sue is obviously the author's favorite, she often comes to be disliked by the audience. Why? Because she is unrealistic, we can't relate to her, and she has only one dimension: perfection.

The Mary Sue is frequently the result of the author placing him or herself into the story. That's why authors have trouble understanding why everyone else dislikes the character. "How can you not like her? She's perfect (like me)!" It's a little egotistical, but hey, we're all a little egotistical. Except me. I'm a paragon of humility.

But back to the original idea. Why is no one smart and beautiful in fiction? More generally, why is every smart person in fiction either: a) lacking common sense b) totally awkward c) ugly and weak or d) crazy eccentric? Have they never met a genius (like me)? If they had, they'd know that smart people are completely normal, except better in every respect. If I ever had the chance to write fiction, I would portray nerds realistically: we're practically oracles with both our earthly and unearthly wisdom, we dominate every party we set foot into, and there is no problem in the world that can't be solved by a bunch of people like us. Everyone will love us, and want to be us, as we achieve ultimate cultural power!