Why are we just friends?

Im bored so I figured Id make a post. I met a girl 3 months ago. It started out as friends with benefits, but over the past 3 weeks we’ve been together almost every day and have really gotten to know eachother. We have the same interests and personalities, so we get along great and love hanging out with eachother. We’re even planning a vacation and road trip together with a few of our friends. One day she told me she really liked me (as in more than a friend) I told her I really liked her too and that I saw potential between us. She agreed, but said that there is a guy at her college she is “kinda dating” From what I’ve heard she argues with this guy often and I can honestly say he is fat and ugly. WTF is up with this? I’ve never been in this kind of situation before. Is it just another case of “nice guys finish last”?