A couple of things you need to know:
- For the average girl, only about half of all guys will find her attractive, and of them, 9 out of 10 guys who find the girl attractive will ONLY want sex with her - she doesn't "click" with the guy in the way that he'd want her as a girlfriend, but she is still attractive enough for him to want sex with her. To put it another way, 50% of guys wont' be interested in her, 45% will only want her for sex, and 5% will want a relationship (and sex) with her. Keep in mind that girls generally only want relationships with 5% of guys, so in that respect they're about the same.
- The above statement is generally true, but it's also an "average" of all guys. In reality, all guys are not equally attractive. The more attractive a guy is to girls, the more options he has with girls, and the less likely he is to commit to just one girl (and when he does, she's usually a VERY desirable girl). Thus, as a girl wanting a relationship, the more attractive a guy is, the harder it will be to get a relationship from him - much like it's harder for guys to get "just sex" from a really hot girl, especially if the guy is "average."
- College happens during the very peak of a guy's sexual peak years (roughly 16-25), and being away at college is also usually the first time they've had freedom from their family and "friends" (i. e., people who will rat them out to their parents) - so they tend to go wild and want to party and have fun. They also know that after college, they'll have to start the job grind - from the bottom rung in most cases - so they want to party hard in college.
So... it's a tough environment to begin with, and much tougher if you want a popular/attractive guy (who has lots of options) or a party boy. If you're looking for a relationship, you need to be looking more at the "serious student" types and/or those who are less conventionally attractive and/or are shy and have fewer options. They're the ones who are more likely to be interested in a relationship.