Pregnancy does happen with birth control, true, but not at the rate we see it happening on this board.
I have raised a child to adulthood and I was a teen mom. I was 16. I wouldn't wish that on anyone. The road is harder than anyone *thinks* it is going to be. And it isn't just about being a teen mom, it is about being the youngest mom in your child's school, about the constant prejudice you face when you go to the grocery store, the judgments that you must be a bad mom because you are so young. NOT TO MENTION the fact that these cute little babies grow up, they become the teenagers you are today. And the whole cycle starts again.
I advocate children being children and living your life (and what a fun life it is!) until you are mature enough to have your own health insurance, buy your own cribs, drive your own car, can vote, can drink, can be an adult.