I believe they procreated because that's what you do in nature. On a deeper level, they humped to ensure they had another member of the tribe to gather food and ward off threats.

As for people having children, isn't it also about hope that a future generation will put things right, that life will be better? And the need to pass on your legacy, your wisdom is pretty strong.

The world is always burning from threats (animals/war/desease/environment), we just have global news to make it seem like its happy every moment. And yeah, global warming is real, its moving faster than ever, but there's always been cycles of ice ages and humans always survive.