While the first thing is a fair point, my point was that they were capable of conducting themselves as men at that age if they were raised to be men. I think we make a lot of excuses for ourselves or our kids. By the time you're 16, you should be smart enough to stop making ridiculously dumb decisions like robbing a store for instance. But if your parents aren't there and guiding you and you're influenced by dumbasses, you'll be more likely to do stupid stuff like that.
You're right, we don't have to be emperors at 18, or at all. But my point was that at that time, they were groomed to be a leader from birth in the event they ended up being a young king or ruler of some kind. The least we can do as men, is teach our kids to behave like adults by the time they are in their mid-teens. Prison is full of people using the excuse that their father wasn't around to show them how to behave or discipline them, so it should go without saying that people should be better parents is all I'm saying.