Tamerlane:
The basic problem I have with this is just that if we’re going to have a legal age of majority, it should be ONE legal age of majority. I’ve always found the scattershot approach kind of silly. If you can vote at 16, you should also be able see an R-rated film (or X, for that matter), join the military, sign legal contracts, drink booze, smoke cigarettes, get married, consent to sex and all the rest of it. If you (or society) don’t think 16 is sufficient for any of those then it should be set at 17, 18 or whatever.
Regardless it is not like giving 16-year old the vote would make a bit of difference in elections. 18-year olds already don’t turn out much, 16 and 17-year olds would be even worse.
The issue is we have multiple ages which are milestones of maturity. In the US ages 16, 18 and 21 are big ones. But there are other ones too. 25, 30, 35, 55, 59.5, 65, etc.