Sense, Nonsense, and Not-Sense

I seriously don't get this fascination with "nice guys" and "getting ass". I thought it boiled down to one of two possibilities: 1) Nice guys don't do casual sex. It's a circular argument but it goes like this: Guys who sleep with the "nice girls" are just taking advantage of the girls and ergo are not "nice guys". Nice guys are therefore the ones who make friends with the girls, do their shopping (resenting it all the way), refuse to let the relationship progress further (because it wouldn't be a nice guy thing to do to hook up) and then go back to their rooms and download porn. Because porn is acceptable nice-guy behavior. The "nice guy" club reads "virgins only" on the front door. OR 2) Girls can friends with you even when there IS NO ATTRACTION. At least in that direction (and she probably assumes the same is true in reverse). She doesn't view you as sex on legs, hence she can comfortably go bra-shopping with you without feeling embarrassed, hence no sex for you after you get to see her prance around in her underwear.