Kind of a weak argument, we currently ignore the first part almost entirely from a legal perspective, I don't remember the last time a child or parent got in trouble for a kid sneaking booze under age. They get in trouble for the things they do while drunk, but not the drinking itself. The parents get talked to, but unless they bought them the alcohol there's no repercussions.
As for the the weddings, they are still legal with no effective minimum age in 4 US states (and there are multiple marriages a year as young as 12) and about half the states only restrict it to age 16+