No, it should not be lowered. While it's not perfect, it helps keeps immature kids from drinking before the fully understand its effects on the body and judgement. Of course, this is the same reason that in most places, you cannot rent a car until you are 25.
I don't know a single person who the drinking age stopped from drinking. The only people under 21 who don't drink are those that have no interest in it whatsoever and don't want to even when they are over 21. Not to mention statistics in universities show that there is absolutely no difference in alcohol comsumption for those 18-20 and 21+. That's true in my case, I don't drink any more than I did before I was 21.