Yes, but... keeping the age at 21, lowers the odds of YOUNG, inexperienced drunken kids on the roads.
I sincerely doubt that.
Allowing young people to drink amongst adults sensibly would not only take a lot of the mystique out of it, it would mean they are much more likely to drink responsibly and not drive afterwards.
By having the age as ridiculously high as 21 will not only make kids want to drink more, it will make them have to do so out of the view of adults, and that's where the problem lies. And they
will get hold of it. Someone somewhere will boot for them. You're also sending out a truly bizarre signal to the kids too. It tells them that all laws are stupid and authority is not to be listened to.
Why 21? What possible reason? If a kid can drive a car at 17, kill in the army at 18, buy a house, get credit at 18, marry etc etc, why not drink? does the US have lower instances of youth and alcohol related incidents than countries with a lower drinking age? I very much doubt it. And what about narcotics? If they can't get hold of alcohol to experiment with, they'll get hold of something, that's for sure.
Here's a little story. I was arrested at age 17 for marijuana possession. After a night in the cells and a heavy interrogation, the police gave me a caution thankfully, and a bunch of govt produced pamphlets telling me marijuana gives you leukemia. Leukemia!! Now, everyone on the planet knows that's a crock of shit. What effect do you think that lie had on me? I'll tell you, it made me not believe a single word anyone in authority told me about narcotics. Within a year I'd tried every single drug under the sun. Why would I not? The official stories about the drugs weren't to be trusted. I had to go find out for myself.
And that's the problem. Young people need guidance. If you don't guide them, they'll go and find out anyway. And in the case of alcohol, that leads to much more danger for the kids and society as a whole.