There are both cultural and likely biological reasons, some of which you doubtless know, but (I hate to break it to you) knowing doesn't necessarily help.
Biologically, intelligence can mask other undesirable traits. You might be nearsighted - before corrective technology - but very bright, and have figured out ways around the problem, adjusted your lifestyle, etc., so that you are high up on the tribal totem pole in terms of actual well-being. But, intelligence for men is inherited almost entirely from the mother, while inheritance of physical traits are generally 50/50 from both parents. So, the fact that you are smart does your boy children no good genetically, while they very likely will inherit your nearsightedness.
So, any woman who is sexually turned on by geekiness - or at least geekiness accompanied by a high IQ - is not serving her genetic interest. Intelligence is thus biologically a natural turnoff. Of course, daughters inherit everything from both sides, but who cares? Mothers and fathers both put much more value upon sons in just about every culture that ever existed, which is a separate line of causality genetically, summed up with the notion of just how many offspring (as in the revelation that most of the human race alive today can count Gengis Khan as an ancestor) downstream will benefit from a really terrifically endowed daughter, vs. a mildly endowed son who is sexy - i.e., not intelligent, but able to survive anyway.
I suspect that women are even attracted to really stupid or mentally defective guys, which is why rock stars go out of their way to behave as if... If you're a real dummy, but make it in society anyway, then you must have really good genes in other departments.
This also ties into the kind of strategies that women use to get a man, usually involving fairly transparent deceptions. A guy with intelligence is also likely to have principles and treat women as fairly as possible. Dumb women, no matter how pretty, will ultimately bore him to distraction. So, women who behave duplicitously or constantly play head games or insist that they be treated like queens, instead of fellow human beings or friends, get the stupid, immature guys, again with the good compensating physical genes. This is one reason why, despite all the rhetoric, women still go for abusive jocks over tender-hearted geeks, almost every time.
I'm certain - because I've seen it - that some women in each generation reject this aspect of their sisterhood and play it straight with men, and end up terrifically happy with some intelligent guy. However, statistically they don't matter.
Consider that for many generations, getting married was like committing suicide. If you remained a spinster, you could expect to live 50 or more years. But if you had children, your life expectancy dropped to the 30's, due to childbed fever primarilly.
So, why get married? What a STUPID thing to do! But those women who didn't have kids, didn't pass on their bright idea to their kids, right? Those women and societies that provided justifications and social mechanisms - pressures, stigmatization, etc. - (your sacred role as a MOTHER!) for motherhood and marriage, survived - at the cost of the women's health and longevity, but so what? The irrational women created the women's culture! And that is what we have today.
And the rare woman who breaks free of all that preprogrammed nonsense has fifty smart guys bidding for her.
You can't win. Or maybe you could take some dumbing pills. There are drugs that permanently lower your intelligence, but just taking valium might be enough. Or extacy maybe?
