No one knows how to increase the birth rate. And all the studies show that immigration increases the budget deficit, not reduces it (at least in that way in which it is being implemented now).
No one wants to implement it.
And it makes complete sense. The reality is having a child kind of sucks for a woman, and I, nor anyone else, can blame a large portion of women for just saying "eh... no". I would probably say no, too, although it's hard to tell, because I'm not a woman.
Having children was once a boon, because conditions were shit. Now it's a burden. So, people will treat it as a burden.
Either make it less burdensome or revert women. Nobody wants to do the latter, so we must do the former. We have to invest in children, because children are a Nation's investment.