Because it's not always the case that people don't want to have children but they are instead constrained by their situations, which can be alleviated by free daycare, education, healthcare, etc.
I think what you are doing is assuming that the current state of the system is all it can be and that people's decisions they make resulting from the current system what they truly want.
At some point I question why people want to have children if their idea of "raising a child" is shipping them off as early as possible to have someone else raise them. Sure, situations vary, but it feel like these sorts of incentives eventually encourage parents not to parent.
Broadly that falls under the category of "development" and will have the opposite effect, lowering birth rates, and that's fine. Finland has all of that and more -- in addition to high wages and low inequality. They'll even mail you a box of supplies when you have a child. They have a birth rate of 1.48 vs Canada's 1.5 vs US 1.77
Yes, we should have those things.
No, they won't increase birth rates, they'll probably drive them down. I know it's counterintuitive, but they data is very clear.
I think what you are doing is assuming that the current state of the system is all it can be and that people's decisions they make resulting from the current system what they truly want.