Two is that 16 year olds aren't at the age of majority, so it would be a little inconsistent to say they're not even competent to govern themselves but are somehow competent to help govern the country. The whole point of high school is supposedly to prepare children to become citizens, so if they are already prepared before completing high school, what's the point?
You make an excellent point here, though I daresay that our country's education system has forgotten the point of high school. Too many people treat high school as little more than a stepping stone to college, and the schools are happy to play along with that idea.
