Most people in developed, Western countries get free birth control (and all other medical necessities) from the government. This is funded by their taxes.
This is also true of US citizens using Medicare.
Further, taxes pay for sex education at public schools, CDC awareness campaigns, and other
> Could declining birth rate be a sign of a better society that values quality of life over quantity of offspring genes?
Yes. What I'm saying is that the "better society" part is funded by governments (especially in Western Europe and Canada): public health programs and social safety nets decrease economic reliance on children, which reduces economic motivations to produce them. Fewer children also die, reducing the need to already have "extra" children to replace them.
> Perhaps if incentivizing smaller families with UBI for life will be a better policy than incentivizing large families?
UBI may make sense. I don't know. It depends on the specifics and hasn't been extensively studied.
However, I'm still trying to understand why you think anyone is "incentivizing" large families. Who is doing it and why? What part of the government is trying to increase the birth rate?