Imagine a society where anybody who has bad luck is left to suffer. Perhaps your business fails. Or you get sick. Or you are born disabled. Bad luck becomes a life sentence of misery. So anybody with a sick relative or a failed business has great financial pressure to steal, cheat, let people die in "accidents", etc.

This creates a culture of secrecy and distrust where nobody tells the whole truth. Above all, most people take fewer risks. Such a society will have very poor economic growth.

So caring for the weak creates wealth. But only if the weak actually benefit: good intentions are not enough! So the presence of the sick person being cared for is what generates wealth.

Ground rent measures this, so societies can earn money through being good.