You're plenty attractive. Maybe you just aren't a very warm person, y'know? Maybe you need to work on smiling more and making guys feel comfortable so they'll be more inclined to flirt.
I really can't imagine why else you wouldn't have guys asking you out now and then. Are you arrogant? Of course you probably don't think you are, but has anyone ever described you as arrogant? I can't imagine that intelligence would drive men off unless you're kind of an a-hole about it. Sure, it might discourage idiots looking for a naive chick to use and discard, but that's not what you want. Intellect ought to attract intellect.
God, so atrocious in the Old Testament, so attractive in the New--the Jekyl and Hyde of sacred romance.
-Mark Twain
If people are good only because they fear punishment and hope for reward, then we are a sorry lot indeed.
-Albert Einstein