While society would no doubt benefit from outing abusers, teen births as a whole are a tiny portion of births. 10% of a small number is a small number. Given

While society would no doubt benefit from outing abusers, teen births as a whole are a tiny portion of births. 10% of a small number is a small number. Given women cheat at the same rates as men, blanket genetic testing would break up a significant amount of families. That's why some countries (France for example) ban paternity tests.