I think it’s true that guys are able to get laid without having any emotional attachment but let me tell you that there are plenty of girls too. I think that this is more a function of how you were raised and how you learned to relate to people from the opposite sex than from any innate instinct (good one eh, innate instinct, as if an instinct could anything but innate).
I read a much more holistic description of attraction. In the first place, there is the existence of a sexual impetus and it can be explained biologically, philosophically, spiritually etc. However, what we are doing is constantly looking for that person that corresponds to the image of what our other half should be like. This image is a combination of all the people we have met before who would somehow fulfill some of the needs we develop while growing up. Therefore, we all have a benchmark in our heads against which we evaluate potential partners.
My two cents.