In the United States, citizens are considered 'adults' and assume many responsibilities at age 18.
At age 18, citizens are given rights such as:
the decision to get married,
sign legal contracts,
vote for the leader of our country,
but they are unable to decide whether or not they want to have a glass of wine with their meal.
Also, citizens are required to...
sign up for selective service to serve their country and
be tried as an adult in court.
All of these rights given to 18 year olds are life altering and impactful. The fact that drinking alcohol is not one of the privileges given to citizens along with the other rights is extremely inconsistent.