Let's face it, everything you tell a teen not to do, they're gonna wanna do anyway, be it sex, drinking or drugs alike. So why not just let them do it at home where you could monitor them, ensure they didn't go anywhere, or if need be cut them off, than in a place where you can't. It just makes sense, and instills a trust in your kid, and teaches them how to be responsible about what they do. Outright telling them no will drive them elsewhere and no good will come of that. It is much better to allow them to do it in the home.
So yes, I think it's best to let teens drink at home than having to worry about them drinking elsewhere and driving drunk afterward.
Let's face it. Teenagers are curious about drinking and drugs. It's far better to monitor your kids' behavior in a controlled setting instead of at a wild party. I'm not saying parents should get their kids drunk. If your child wants to experiment with alcohol, do it in a systematic way. Start with beer and see how they like it and go from there. The look of disgust on your child's face will say it all. Another thing to keep in mind is that kids who drink have parents who drink.
In general teenagers should not drink at all, as their brains are not fully developed and alcohol can lead to even poorer judgement on the part of the teenager. But teenagers will find some way to do what they want no matter what, so it is better that they are in a controlled environment while they do it. Drinking at home with responsible parents nearby is a better option then having teens drink at unsupervised parties and driving home.
Allowing underage teens to drink at home is just asking for trouble. It sends the message that rules, or laws, do not have to be adhered to in the entire context of their lives. Worrying about a child driving drunk is worrysome, but parents need to communicate to their children and also keep them closely supervised.