*Elon Musk wants everyone to have big families like him — but who's going to pay for them?*

It is rational to choose not to have children because raising them is so expensive. But if that is the main thing that convinces people to avoid having children, then survival of civilization will depend on making the children of poor people grow up in poverty.

We need people to be even more rational, and choose not to have children because the world can't support them. Plus, it's dangerous and painful, etc.