Why is that? Australia did (or still does?) have monetary incentives to have more children, completely backwards...

I think that is maybe distasteful. A monetary incentive to not have children is like advocating state-sponsored neutering of people. And since its money, who do you think would be affected for such things? the rich?

So basically its the very concept of paying poor people not to procreate, so that the current existing people have a 'nicer time' (which is actually also economically incorrect).

Its super gross.