Which is exactly how high schoolers get a hold of beer, incidentally. Plus, 14 year olds can have 21 year old (or older) siblings who are willing to get them stuff, too.
I bet if there was a requirement for all of these things to be set to the same age as basically "the age of majority," they'd back the fuck off since it would mean raising the voting age back to 21 and military service age up to 21.