Raise the driving age, keep the drinking age where it is. People who really want booze are gonna get it regardless of the law, so the best we can do is let them know there are legal consequences for acting like a moron. Wanna get drunk? Fine, but if you hit somebody with your car, you're going away for a while. Stupidity can't be condoned. Unless somebody held you down and forced the beer down your throat, only YOU are responsible for when, where and how much you drink.
I like the age limit where it is. People under the age of 21 act stupid enough now-they don't need any beer helping them.
And I realize maturity and age often aren't connected at all, but it's not like the guy at the counter of a Quick-O Mart can tell how "mature" you are by looking. A blanket age limit is needed, so that nobody can claim unfair treatment. And since, as a general rule, people older than 21 are more mature than people younger than 21, it seems like a fair law to me.