That's because none of the ads have heeded the peer-pressure evidence/advice I talked of (re: poor ad campaigns). If the ad campaigns stopped suggesting that drinking was a widespread problem (without using statistics, because lying leads to backlash), and suggested that it was a very narrow problem, then more people would feel isolated from drinking. By creating the perception that only a small select number of people drink, then people will feel less compelled to drink.
In Texas, there was a clean-up program called "Don't Mess with Texas". One of the successes about it was that it heavily implied that your wrongdoing was messing it up for everyone else. It appealed to peer-pressure conformity, and exploited the fact people follow their perceptions, rather than their reality.
That said, these perceptions might be drawn from shows like Gossip Girl and the OC, so unless we want to move into the band of censorship to promote a culture we want, then this may be impractical.
Generation Y is as skeptical towards scare tactics as they are towards advertising (hence the hate towards Daniel Dobos, Mental Blank seminars -- lots of people hated the free seminar because he tried to sell something for 30 minutes!)
(N.B.: Not saying that this mentality is flawed - it's completely fine. Advertising (of products) is going to be toppled on its head in the next generation or so - read Seth Godin if you want to hear about this.)