Because society needs children. Or at least, it always has in the past. And given that people are still prone to tribalistic thinking, it's a hard belief to was

Because society needs children. Or at least, it always has in the past. And given that people are still prone to tribalistic thinking, it's a hard belief to wash away. You may not notice it if you live in a relatively homogenous culture. But when your 'enemy tribes' plan to extinguish you by outnumbering you, it's a real concern.