Most Helpful Guy
In my experience, girls tend to like guys more that already have girlfriends. It shows that at least one of their kind has deemed the guy alright, and it also gives women the ability to boost their self-esteem; if they can "steal" another woman's man, it makes them feel "better" than that woman.
The result is that some guys will start out with a girl they don't really like all that much, with the sole intention of using them for this purpose. The girl is really only there as a crutch until a more permanent solution can be found. In other words, an upgrade.
This system works surprisingly well, which is part of why you often see the dumbest thug type guys with really attractive women. They didn't start out with a nine; they started out with a five and worked their way up.
Sad, but true.