What you're describing is tragedy of the commons. No negative consequences to not having children, but big negative disproportional cost to the parents raising

What you're describing is tragedy of the commons. No negative consequences to not having children, but big negative disproportional cost to the parents raising them. With disproportionately privatized losses and socialized gains. People often say you shouldn't have kids for your own retirement. In the ultimately hypocrisy, they often mean kids will be for everybody's retirement (when they're forced to pay social security taxes as adults). The economic incentive is to let others have kids and shoulder disproportionately the costs, while you can free ride and "not have negative consequences." Immigration doesn't solve this problem at the system level as removing children from foreign tax pool into our domestic pool shifts benefits from one elderly person to another.