I'm 21 too,
My issue was never drinking as much as it was smoking enormous quantities of weed and messing with other drugs. I quit the weed/drugs 5 months ago but still drank up until a few weeks ago. I decided that I didn't like drinking much at all and decided that I wanted a life free of all substances.
I get the whole "it seems like the thing to do in college" mentality, as I struggle with it a lot. It's tough. I go to a huge party school where all people talk about is how drunk they got the weekend before, and it's honestly getting irritating. With that being said, it gives me an opportunity to see just how stupid people seem when they're hammered or high or whatever. I liked the counter cultural feeling of doing drugs when I was in high school, but now that I'm in a place where everyone imbibes without restraint, I feel unique for being sober, and I like it. I get it, it sucks at times though. Just think, once we graduate, we'll be a step ahead of the people who went wild in school.