I think it has to do with the fact that most women that I am friends with are professionals who stayed in school anywhere for 6-10 years post-high school and so that skews the anecdotal results.
...The one thing that I have wondered for a while is why abstinence until marriage is even supposed to be a good thing. It is commonly cited that sexual incompatibility is a top three reason for divorce - is it not then in the interest of a good marriage to be sexually compatible? I am not saying you need to go out there and sleep with a hundred people, but if you are in an adult and committed relationship and you plan on marrying this individual, why NOT have a sexual relationship with them?
Well, yeah, I didn't personally know anyone who got unexpectedly pregnant in college or grad school either. Nor, so far as I recall, did any girls get pregnant at the second high school I attended (prep-schoolish Orthodox yeshiva populated almost exclusively by wealthy Brooklynites who'd spent their entire lives in such environments, as opposed to my former high school in Mississippi, which was 100% free-lunch eligible and though the best school in the area, definitely not an everyone's-headed-for-6-10-years-more-study kind of place). Educational aspirations and socioeconomic background definitely matter; in fact I'd be tempted to say more than any other variables involved.
Abstinence before marriage is a good thing insofar as one wishes to get married, engages in committed relationships with the general hope that this person may turn out to be the right lifetime partner (which is not to say casual dating is ruled out), and views the sexual self as a deeply intimate thing to be shared only in the most deeply committed relationship. If like me one also happens to be an observant Jew who wishes to always live in an observant household, then a factor of even more importance is that Jewish law requires abstinence--we observe what the law stipulates, see following that discipline as an end in itself, and don't usually spend a lot of time creatively rationalizing it, save for rare exceptions such as if it becomes clear that following some particular law as interpreted is doing serious damage to its adherents (e.g. proscribing homosexuality). I can't relate at all to precious-wecious 'purity pledges,' flowery teen lit presenting sexual desire as epic 'trial' or 'challenge' from God/Satan, or tearful testimonies from drug-addicted nymphomanic pornstars who've had 50 abortions about how if they'd only not had sex with that needy pimply-faced boyfriend back in high school and stayed 'pure,' then their lives would've been sooo much better.
I really don't get the "compatibility" argument, and honestly have never understood what people are on about who cite it as a reason why it's supposedly bad for you to wait until marriage to have sex (we did). We've been married for more than 15 years, have three kids, and without getting TMI, personally I would rate that aspect of our marriage as very active and very satisfactory. In the meantime, many other married couples we knew (ones who hadn't had sex beforehand, AND ones who'd had numerous partners beforehand) have gotten divorced, with, yes, complaints that sex had become dull through to nonexistent ("incompatibility") being a major factor. As far as I know all these couples were
initially quite pleased with their sex lives, so I can only conclude that "compatibility" more or less turns out to be vague and sloppy shorthand for "This relationship just doesn't work for me anymore, and that comes out in the bedroom among other places." Sexual relationships are dynamic, anyway; no one wants the same things the same way year in and year out, bodies change with age, some relevant emotional states will be more predominant and intense one decade and others the next, etc., etc. Like with anything else in a healthy marriage, experiencing change and occasionally frustration together just comes with the territory.