The laws need to be enforced to work, I would never suggest otherwise. The fact is when the laws are enforced it becomes difficult for teenagers to buy liquor

The laws need to be enforced to work, I would never suggest otherwise. The fact is when the laws are enforced it becomes difficult for teenagers to buy liquor themselves and, absent people who make a living selling liquor illegally (these people still exist in some remote parts of Alaska, and in some very poor areas of the rural Appalachians, but not really elsewhere), teenagers will have a difficult time finding a reliable source of alcohol (Joe's older brother who goes to college may pick you up a keg once in a while for your parties, but Joe's older brother has better things to do than buy teenagers booze all the time, even if he's gouging them) On the other hand, reliable sources of pot is easy for a teenager. The people who are willing to illegally sell pot to teenagers are already selling to a larger more affluent audience illegally as well (adults). Basically: Selling alcohol to everybody illegally: Laws are enforced: profitable, and risky. Laws are not enforced: profitable. Selling alcohol to only adults legally: profitable. Selling alcohol to only minors illegally: Laws are enforced: not profitable, and risky. Laws are not enforced: not profitable. Selling alcohol to adults legally and minors illegally: Laws are enforced: profitable, but needlessly risky for what you gain. Laws are not enforced: profitable. Given that you want to restrict childrens' access to substances, you want to be in a position where no adult considers it worth it to sell to children. The best place for that is "selling to adults is legal, selling to children is illegal, the law is enforced".