You have to ask yourself "What is the benefit to society by lowering the drinking age to 18?" I can't think of any benefits, but there is no problem coming up with good reasons not to.
More drunk driving deaths
More alcohol influenced altercations (drunken brawling)
More cases of alcohol poisoning
More cases of domestic violence
More influence on even younger teens and children to experiment with alcohol
More tax payer dollars for the courts to hear these cases
Higher Insurance premiums
and on, and on and on.
As a police officer, I see the effects of alcohol on society every single day and am more convinced than ever that NOTHING good comes from consuming alcohol. There is no such thing as "responsible drinking" and that term is nothing but an oxymoron. Once you take a drink, your senses start becoming affected and you no longer can be responsible for your actions. All of the excuses for wanting to consume lots of alcohol is nothing more than copouts for people who are miserable, unhappy or unsatisfied with the natural joy in their lives and need some form of stimulation to escape reality.
So, I guess my answer would be NO, I don't think we need to lower the drinking age to 18. :)