In the United States of America, an eighteen year old can fight, kill, and die for his country, elect political leaders, and buy tobacco. However when it comes to alcohol, we are still treated like juveniles. An eighteen year old can walk into a gun store and make a purchase, yet we can't go out to a liquor store and purchase a case of beer. It makes no sense when a person looks at the big picture. The government should not be able to pick and choose what will be regulated when a minor reaches the age of adulthood, it should be all or nothing.
From the day you turn eighteen, you are no longer a minor in the eyes of the government, or so they say. The government grants you the rights of adulthood, for example, by allowing the opportunities to vote. This gives the new adult a voice in the government that was never an option before the age of eighteen. However in return, you must register for the draft, allowing the possibility of being forced into the army and sent over seas to fight, and even possibly die for your country. There are other rights you acquire also. For instance, you can purchase a firearm, you are also seen as responsible enough to start a family and therefore take responsibility for bringing others into this world, along with the capability of adoption and abortion without answering to a parent or guardian. And in accordance with these great abilities you are also now tried as an adult in the court of law. Turning eighteen in America creates a new existence of responsibility in oneself, with both ups and downs. Therefore the legal consumption of alcohol should be permitted from the age of eighteen, since drinking is simply a question of responsibility.
All of this is not to say that there is no validity in the arguments of the other side, the side that calls on the Minimum Drinking Age Law of 1984 as an example for their cause. Regulation is understandable, because there are consequences to a lower drinking age.