Okay, so on an actual serious note -- Historically, this has actually been the lever that's been pulled by government in order to control population growth.
The problem is that we've grown so much as a society that we now realize that bodily-autonomy is a human right.
There are ways they can promote population growth, if that is something we really want. Better and free school lunches would be a start. Childcare. Pre-K education. Free college. Health-care. And generally a more wealthy middle class.
The biggest reason people are having fewer kids is money.
This 100%. We and many of our peers with a kid are one and done in the current system. But if we could afford college educations for multiple kids, get adequate parental leave, access to early childcare that doesn't cost an entire paycheck? That would change the decision quite a bit.
But also I'm happy to have fewer kids and let more immigrant and/or refugee families with young kids move here too. Solves the labor shortage and provides a much needed influx of fresh ideas and culture, not to mention getting some folks out of dangerous situations. Somehow all of the people who want to "save the children" are extremely silent on that front when it's children moving to another country for a better life.