"In the past, this was a reason to have children, because you needed somebody to help out and look after you when you were old"

I live in what is supposedly one of the happiest, wealthiest countries in the world, and even here few people trust the healthcare system to take care of them when they're old. My grandpa would have almost certainly died years ago if he had no children to look after him.

It's still valid, if selfish reason to have children.