I've always looked at it from the baby's perspective. It seems unjust that we would deprive our youngest citizens of time with their parents during such a critical stage in their life.
IE, train and treat parenting as much of a profession as it honestly rightly deserves, let people specialize and pursue a career in parenting, and then have them be parents as a full time job, paid the same way public schools are.
Because lets be honest - humans evolved to be carried around by their parents in communal groups while nomading around Africa. Its why babies cry when separated and are designed to be constantly attached to someone for most of their first year of life. They aren't even meant to sleep apart from their parents. There is enough sociological evidence that pretty much any form of the stereotypical family unit in any socioeconomic sphere causes trauma to infants because of how they are deprived of their biologically imperative socialization and physical interaction. It goes so far as there being evidence that babies become so anxious because they are stationary - they have a biological impetus to move, that a moving family is safe and to stop moving is dangerous. Its why most calm down if you walk them around in circles holding them.
I think there is also an argument that subsidizing reproduction when there is appreciable demand to immigrate to your country is at least racially biased if not wholly unethical, but thats another ramble.
It is really astonishing to see this comment again and again on this thread. New human beings are necessary.
This isn't a black and white or moralistic "with or against me" topic. Every society basically independently has to evaluate how much it wants to divert capital to produce babies. Many nations - ie, China, India, etc - have or had programs in place to actively disincentivize reproduction.
I'd just as easily argue that subsiding reproduction when your country has foreigners wanting to immigrate as being unethical. If there are people out there right now that want to come and fill the holes in your society left by a replacement deficit, how is it just to instead pay your own people to replace them? Its largely why Japan is in its replacement crisis - the nations staunch ethonostatist view against immigration.
(And maybe even help cover your own retirement?)
It shouldn't, but if your quality of life is being diminished, that's not the kid's fault, nor the mother's.
That's management's fault.
What you can't justifiably do, however, is complain about the specific instances in which you pay for a benefit for someone else without acknowledging all the other ways in which things flow in the other direction.
My favorite example is road costs. Suppose I don't drive a car. Why should I pay for road infrastructure? Because I realize that even if I don't personally drive a car, I benefit from a society in which people and property can be efficiently transported without having to pay the owner of each and every road a toll.
What about schools? Should people without children not have to pay taxes that go toward schools, because they don't "benefit"? They should, because everyone should realize that even if they don't have children, a modern society needs educated citizens to persist. The same reason applies to supporting those that do the work of raising the citizens of tomorrow. (Which you, if you have no children, might mistake for leisure rather than a job.) Presumably you, when you're in your 80s and 90s, would like there to exist people of working age that can take care of you?
Let me tell you, it definitely is not.
If you will be having kids why not save up to be away from work for a year and the take leave paid by your own family?