In the early 1980s, the shift of the drinking age from 18 to 21 significantly decreased drunk driving fatalities (even when you control for other factors). While it’s often argued that it would make more sense to have a drinking age of 18 (the age of legal independence), the plain fact is that the higher drinking age has saved a lot of lives. Because of this, it’s very unlikely that the legal age will be lowered to 18 anytime soon.
 See study by Fell et al. as well as Hingson, Ralph W. and Aaron M. White, “Costs and Consequences (Morbidity and Mortality) Associated with Adolescent and College Drinking and Related Problenms” and McCart et al. “The effects of minimum drinking legal age 21 laws on alcohol-related driving in the United States.”