I do not in any way doubt that teen moms love their babies, but having them can severely impede their ability to pursue education. If they have to drop out of high school to have their baby, it's enormously hard to get back on track, and to pursue further education (college, tech school) to land a fulfilling and lucrative career. They'd be much more vulnerable to entering (or continuing) a cycle of poverty and low education, which will increase future unplanned pregnancies.

responsibility is good for us and it gives us purpose don’t you think?

Sure, and some rise to the challenge. Others fall totally flat, with steep costs to the child.