Responsible Person?

In the United States, the legal drinking age for all 50 States and the District of Columbia is 21 years of age. The drinking age is 21 because the powers that control our government decided that when one becomes 21, one is magically transformed into a responsible person capable of handling the burden that comes with the right to consume alcohol. The drinking age is too high in this country. Why enact laws to prohibit an act that will be ignored by many of our peers?