I had such a good time in high school, I didn't want it to end. I wasn't celebrating at my prom; it was a sad affair -- I knew I'd either join the military or move to a far-away city and won't get to see my friends every day (some of them were still in high school), won't get to play with my band. And it did play out like that.
Anyway, I still don't get what's there to celebrate, but I guess many think growing up and growing old is good for them. I suppose many dislike going to school, dislike lessons and teachers. Maybe they didn't get to have such good friends, I don't know. I suppose they also thought that growing up meant not being told what to do. Talk about unpleasant surprise on that front... :)
With regard to drinking alcohol I tend to agree with the previous two commenters. Perhaps it's not such a bad idea to get it out of your system at a somewhat earlier age.
I myself was a member of the teetotaler's club until the age of 15, when I drank my first bottle of wine while at camp and discovered how much fun it can be. Indeed, one gets totally wasted 3 or 4 times, and then they learn their limit. :)

Most of the prom dresses are simply hideous, I don't know what are those girls and their mothers thinking.