answer:Experiments by various states in the 70s to have a lower drinking age was considered by many to not lead to any responsible drinking by 18 to 21 year olds, and encouraged drinking by those 16 -18. After many many young people died from alcohol related incidents, Congress passed laws banning federal highway tax sharing with states that allowed drinking under age 21. Much of the higher age limit was driven by Mothers Against Drunk Driving (MADD); the law was signed by Ronald Reagan.