Not to be too cynical, but if 16- and 17-year olds could vote, it would be harder for state legislators to pass, say, restrictive driving rules or higher insurance rates for drivers younger than a certain age.
This is exactly why I want the voting age lowered. For too long have politicians, parents, schools, and moralizing busybodies taken rights away from people under 18. Our society seems to think that personhood is dependent upon being 18+. If the trend continues,I fear it won't be long until people are required to be in a school building 24/7 from the day they're born until their 18th birthday and anyone who tries to escape will get the death penalty. Once, teenagers hung out unsupervised, went to the mall, drank, smoked, and had sex without going to jail, and could skip school without being tracked down. But today, people under 18 are pretty much prisoners of adults. Something needs to change. We need to re-examine the way society views people under 18.