Should the legal drinking age increase in the United States?

I feel as if the legal age to drink shouldn't be increased. There are numerous of reasons on why i feel as if the age limit shouldn't be increased. First and foremost the drinking age is already three years more than the legal adult age group and the legal age to purchase tobacco products. These two have the same effect on individuals in different ways. The legal age to be considered an adult in the United states is 18 which means you're held responsible by anything. So if this is so then why can't every adult be responsible for their actions period.