Why are girls attracted to immature guys?

I have been friends with Tommy and Nick for a few years now in College. The thing that still perplexes me is that despite their obnoxious level of immaturity at points, they are far more sucessful with girls than I am. I already threw out the possibility that it has to do with looks, because I am as good looking as them or more so. They are my friends and can be cool, but it just annoys me when they start talking about the most immature stuff. They are both very lewd and often make poop jokes and jokes in front of the girls they are trying to get with. From my perspective of watching this, it seems like it should not be an effective strategy, but for whatever reason they usually end up with the girls, and some of these girls actually laugh at these lame 2nd grade jokes. Why is it that a guy like me who acts his age and tries to be a gentlemen has a tough time with girls, while my friends who act like they are still in elementary school are so successful?