Better still for a discussion of contraception would be an estimate of the "unplanned pregnancy" rate, with no reference to age; but that would be difficult to measure, and lacks the emotional power that is inherent in the "OMG won't somebody PLEASE think of the children" statistic.
Unplanned pregnancy among women over 25 is also and issue and reducing those numbers would also benefit society and reduce future costs in many ways. However, the negative impact of unplanned pregnancies when the mother is a teen is much higher than when the mother is 30. A 30 year old is more likely to be able to handle the situation, the father is more likely to contribute to the upbringing, and the child is less likely to impede the parents education and early career development since those things will be over before the child came along. IOW, society has a rational basis to care about preventing unplanned pregnancies in general, but also especially among younger women and teens.