Many teens can get alcohol as early as middle school, but by age 18, nobody really cares anymore. By 18, most people who want alcohol are able to get it, and many are able to simply walk in and not be IDed. Outside of big cities, few people ask for ID every time.
I believe the legal drinking age should be 21 years old. I think making it an earlier age could be dangerous. Young people will make irrational decisions involving alcohol and could cause harm to others based on those decisions. We should make the drinking age at least 21 years old for this reason.
By and large, at the age of eighteen, men and women are able to vote and expected to be responsible for their own decisions. Even so, a system has been created under which a larger and better-represented voting group (21+) has systematically disenfranchised a smaller and underrepresented voting group (18-20). This is due, in part, to the influence of a militant prohibitionist lobby called "Mothers Against Drunk Driving," who pushed the enactment of The National Minimum Drinking Age Act of 1984, which made states subject to steep highway funding cuts unless they raised their alcohol purchase age to 21.
Not only have all serious studies of the effects of NMDAA found it to have not contributed to national safety, but the idea itself is fundamentally wrong and unamerican. For one, because the federal government does not have the constitutional authority to set a minimum age, it uses a loophole by instead twisting states' arms. For another, it (arguably in violation of the 14th Amendment) violates the freedoms of a subset of Americans who can vote, hold public office, and be drafted into the military.