A lot of people do not want kids not because they don't like kids, but because they feel they're not financially ready to have kids and they are not wrong.
Having kids when you can't take care of them is not a good thing to do, so instead of the Government rewarding families that give birth to children, they should find ways to create opportunities for the people, especially young people.
I believe underpopulation is not as big an issue as they make it seem. Don't get me wrong, I know it's an issue but how many countries can show proof that the economy is slow because of underpopulation? Worst case scenario they open their borders for skilled immigrants.
The biggest problem facing world right now is that intelligent people are having less number of children, while those with low IQ are having plenty of them. And in the long-run, this doesn't bode well for the human race. Look at the following maps:
IQ level by country:

Fertility rate by country:

It is very clear that overall IQ level of human race is going down, and that too at a rapid pace. In the long run, this is not going to bring anything positive for us. There will be more conflict and warfare, and less innovations and inventions.