A lot of the time, people drink and drive because they are coming home from somewhere like a bar, club, or any other alcohol serving establishments. If a larger amount of people (18-20 year olds) can legally drink, there will be more people on the roads leaving bars or clubs. More intoxicated driver's leads to more drunk driving accidents, and more fatalities as a result of drunk driving. In 2002 around 15 million 18 to 20 year olds drove while intoxicated, this does not count the ones who got away with it. The majority of drunk driving accidents involve younger drivers. Studies show that younger drivers are more likely to drive while intoxicated than older drivers. If the number of drunk drivers under 21 is so high now, it would sky rocket if they were legally allowed to drink; this is why the legal drinking age should remain at 21.
There are a lot of actions associated with drinking. Take rape for example, a lot of the time a rape occurs while either the victim, the offender, or both are intoxicated. 45% of rapes committed are by those under the age of 21, 90% of college rapes involve alcohol, and half of all rapes involve alcohol. Although it should not be used as an excuse, alcohol is a huge contributor to plenty of date rapes, especially those among young adults. Because the majority of rapes are done by young people and are also done by people who have been drinking, allowing 18-20 year olds to drink would increase the number of rapes that take place. Drinking alcohol also encourages a person to engage in violent activity, dangerous behaviors, disorderly conduct, and others.
At the age of 18, the brain is still developing, specifically the frontal lobes (or the part that regulates emotions, planning, and organizing). Because of this a person at the age of 18, or younger is more vulnerable to addiction, the chances of depression, the chances of taking part in dangerous behavior or violent activities, memory loss, and suicide.
