If I were mayor of my town I would change the legal drinking age to 18. They main reason they changed the legal drinking age to 21 is because if they didn't lower it, they would lose 10% of their highway fundings. Laws prohibit buying and being out in public with alcohol, but, it's not illegal to drink with your parents, spouse, or legal guardian whom are over the age of 21.
Currently, enforcement is not a priority for many agencies. Police sometimes ignore MLDA (minimum legal drinking age) 21 because of the resource limitations, and obstacles to get alcohol. The time and effort required for processing and paperwork just isn't worth it for some police officers. An estimation of 2 of every 1000 occasions of illegal drinking by peoples under 21 result in an arrest.
According to the website ProCon, there are less drunk driving accidents and fatalities in many other countries with the legal drinking age at 18. Although when the US increased the drinking age to 21, its rate of traffic accidents and fatalities in the 1980s decreased less than that of European countries whose legal drinking ages are lower than 21.
Most kids under the age of 21 are already drinking. They are drinking in unsupervised places where they may be more prone to binge drink and other unsafe behaviors. Lowering the drinking age to 18 would allow them to drink in regulated environments with supervision and the bartenders telling you when you need to stop.