Why shouldn't the legal age be lowered to 16?

In this day and age, 18 year olds aren't even mature or responsible enough to be allowed to do many of the things they do, so why should 16 year olds who are even worse?

legal to do what exactly? EDIT I think there's a sliding scale here. Obviously you're not as smart as you're going to be at 16 but you're not as smart as you're going to be at 18 either. One could say why not wait to give more rights to people until they're 25 and mostly developed. But on the flip side you certainly wouldn't want 13 year olds with the ability to get married or be tried as an adult in court for things like assault. Since you didn't say exactly what it is you want lowered besides "the age in which you're an adult" it's tough to give you a good answer as to what exactly would go wrong. Generally it's just ones personal taste for the sliding scale of maturity. At 18 we can be reasonably assured that most people have matured enough to handle the added responsibilities without getting crushed by them.

Because a 16 year old does not have the mental capacity to make sound judgements. The decision making factors of the brain are not yet fully developed. Therefore, it could be argued, they have diminished capacity.

what, Joining the army? drinking? voting? your no mature enough for many things, that's why it's at least 18 but sometimes it should be 21. And sometimes being 30 isn't enough.

I disagree with your point of debate, but if you want data, do some research on Google/UK. In the UK, 16 year olds are considered adults, can sign contracts, etc. etc.