Though I only did it once (it was mild, I didn't get wasted), I saw the appeal *during.* If you're an introvert, which I am, "drunk you" could become a social butterfly, which is an incentive. Also, I felt that I could make easier friendships and bonds while drunk (if you remember the whole ordeal). It's a bonding social activity thing (getting drunk on one's own however, that I don't get unless you're very sad).
Though what I aim for these days, which takes a lot of drinking for me anyways cause of my tolerance level, is to get tipsy. Your personality inhibitors drop, while you remain in self-control. And you just feel happier (and sleeping in that state is actually soothing).