On one hand, it depends entirly on the person involved. Voting for instance: some kids are very politicalyl aware at 13, while some people really shouldn't be allowed to vote, well, ever.
Drinking? Same thing: one drink every once in a while won't hurt, so some very responsible people would be perfectly alright being allowed to drink at 14. Other people, those who waste their lives trying to get the next bottle of beer, probably shouldn't be allowed ANY alchohol.

That said, we can't realistically expect a governemtn to anaylize EVERY SINGLE PERSON and see what they should and shopuld not do, so some sort of limit has to be established. Some people will get screwed no matter how they do it, that's the way of life.

PS: Fireworks are restricted (on a state by state basis) in America becasue we, as a nation, are friggen' retarded and tend to set our own houses on fire with roman candles.