It's a side-effect of modern societies. This is actually a trend spanning at least several decades. As societies become more modern, they start wanting fewer to

It's a side-effect of modern societies. This is actually a trend spanning at least several decades. As societies become more modern, they start wanting fewer to zero kids. This is actually the main reason why I've never been so worried about those overpopulation predictions, or worried about what happens if the technology starts allowing us to live hundreds of years. Well, if we knew for sure that we would live 500 years (and continue to be young and health), nobody in their right mind would want a kid at 30. And you'd likely still be able to die from accidents for the next 100-200 years.