"However, I do believe studies have shown that women like to do the sex thing with unsuitable but stud-like alpha males, and then settle down with a 'nice' man to raise the other guy's child together."
I tend to agree with this - and I think I see this syndrome being played out in marriages and divorces all the time. For instance, the women I know who married the stud-like alpha males (having being lead predomintly by sexual/romantic attraction) have found that, over time, they have tended not be very faithful husbands and/or not great with kids/family life. The women either put up with this on the basis that they married an alpha male so what did they really expect or they are disillusioned that he is not also prince charming and get divorced.
The women who have chosen partners more on the basis of being potentially a reliable partner and father (ie: have chosen not so much on the basis of sexual attraction) have, indeed, found themselves a constant and faithful companion who is a family man. However what they do not have is the sizzling sexual attraction. Rather like the group above they either put up with this on the basis that, what did they expect, they married a sold 'family man' type and not a Don Juan, or they eventually get sick of the lack of sexual attraction and either have affairs and/or move on.
Anyway, what has this got to do with the thread title? If I was single I would probably be prepared to have relatively casual sex, in the absence of anything better (eg: meeting someone I had a real connection with).
To the poster who wrote that sex is mostly a matter of a penis entering a vagina - well, yes, that is true on a purely biological level. But thousands of years of literature, art, music and much more have been devoted to the subject of romantic love and sex - if it was just about sticking bits of anatomy into other people, that would imply that people do not have emotions and feelings or even brains!
On the other hand, I tend to agree that sometimes far too much is made of sex. So that doesn't answer the question then!