Which is something that we should by all rights do. It's cruel to allow someone to vote or die for their country at 18 but not allow them to have a beer.
The drunk driving issue that was used to raise the age in the first place was a red herring. The way to stop drunk driving is to enforce driving laws not to raise the drinking age.
Either these people are adults or they are not. Either lower the drinking age to the voting age or raise the voting age to the drinking age. I'd vote for the former