After reading, Alex Cheyenne's blog "21 is Less than 18," I feel as though I completely agree. No matter the reason the law of 21 and up could drink legally, it has actually made matters worse. More accidents involving alcohol and long with teens binge drinking.
Now also, why would we, America, give 18 year olds the right to vote, smoke, drive and take part in state lotteries, yet not give them drinking. Smoking is a conscious choice to harm your health. Voting decides our country's fate. Driving has it's harmful consequences, too. And well waste or spend your money on something you may not even have a good chance on winning the jackpot.
Ultimately, why not give them the choice to drink? And as Alex mentioned, it gives them a more public way of drinking, where others can show/teach/assist in good drinking habits. Drinking responsibly is what needs to be taught.