College slang doesn't contain terms for everything the student discusses. However, items that are frequently encountered by college students or are important to college life are often given slang symbols. There are many terms to say something is good or bad and to evaluate persons positively or negatively. This is a good question though and one we are currently exploring empirically in a study that examines speakers' reasons for slanging. The preliminary data indicate that students do slang because it's cool.
Slang is cool in several different ways.
First, it's cool in the sense of being hip and in style. When we speak, we are communicating not only a message about the content of what we are saying but also a message about who we believe we are, our identity. Using slang artfully is a kind of performance and shows that the speaker is in tune with the times. Second, slang is cool in the sense of being acceptable. Students don't slang all of the time.