That's complete bullshit, I know some 14 years that are way more mature than some 18 year olds. Why set the bar so high? It doesn't do anything, if they wanna do it, they're gonna do it.
Same with your absurd drinking laws, 21 is shit.
You can drive, you can vote, you can have sex you can get married etc etc, but you can't drink? Completely illogical.