Decrease the drinking age from 21 to 18

Since 18 is the age of majority in the US for most cases, like being able to vote, to serve in the armed forces, and so on I don't see why the national law should make a citizen what three years into adulthood to purchase an alcoholic beverage. The reasons for raising the drinking age in the 1980's was because of traffic fatalities among drunk drivers ages 18-20, but being in that age group can't be directly linked to as not being worthy enough to handle alcohol. The reason why this age group was effected the most by drunk driving is that they were the most restricted group of people to drink in the country, which forced them to drive further distances to get alcohol, then they would drive a further distance back under the influence increasing their likely hood of getting in an accident.