I think people almost always confuse happiness with fulfillment. Fulfillment is something much deeper than happiness. I can watch an uplifting movie and be ha

I think people almost always confuse happiness with fulfillment. Fulfillment is something much deeper than happiness. I can watch an uplifting movie and be happy because that's a temporary emotion and state of mind. And I can, just as easily, go from happy to angry if someone were to rear end me on the way home from the movie theater from seeing that movie. Parents aren't "happier". At least not by my estimation. But they do seem to be more fulfilled and seem to consider their lives to have a deeper meaning once they have children and become responsible for the safety, care, and development of another human being that relies on them for essentially everything. This is the implicit reason it is done. It's not just the physical (sexual) imperative. And regardless of the status of the planet, if the species is to continue, we at least need to reproduce at a rate approximating replacement. It could be lower - and then we would actually slowly depopulate the planet. But society does need to have birth rates that replace the existing people, or come close to it.