The police have no business arresting anyone for drinking beer or anything else short of paint thinner (and even then only to take them to the hospital.) The law doesn’t get to define someone as only having certain rights and not others. If someone has reached the age of majority then that person has all of the rights (and responsibilities) that go along with that status. When the government plays favorites and defines some people as more equal than others, all of us are made less free.
You can thank MADD for this nonsense. Rather than punish drunk drivers, they lobbied the feds to punish teenagers. The end result was a ZERO percent decrease in the rate of drunk driving and the creation of an entirely new class of “criminals” where no “crime” had previously existed.
I also believe that these laws are actively enforced as a way to punish young people simply for being young.
I’m 37 years old by the way, and a dedicated libertarian.