I'm the kid in highschool that never even thought of drinking, smoking, or drugs. Now I've tried pot (didn't get any high from it so I didn't do it again), smoked a bit, and drink about once a week.
The reason I drink? A reward. I can't have too much. I'm on some stuff that makes one drink = about 3 for a person my size so I make sure I keep it easy. But like when I pulled my failing calc grade up to a C, I rewarded my self with a beer.
I don't see a point of getting drunk though. I can't otherwise I'd likely die, but even If I didn't have the meds holding me back I'd like to remember what I did the night before.