As is stands, parents are able to claim their children as dependents on their tax returns, which lowers their overall tax liability and in effect means that the parents either pay less in taxes or receive a higher return at the end of each year.
Until they reach the age at which they can work, children are a drain on society. They receive public schooling and receive the same benefit from public services that adults do, yet they contribute nothing in return. At the point that they reach maturity and are gainfully employed and paying taxes, they become a functioning member of society.
If a parent decides to have a child, they are making a conscious decision to produce another human being. They could choose to get a sterilization surgery, use birth control, or abort the pregnancy (assuming they don’t live in a backwards state that’s banned it). Yet even if they decide to have 15 children, the rest of society has to foot the bill for their poor decisions until the child reaches adulthood.
By increasing taxes on parents instead of reducing them, you not only incentivize safe sex and abortion, but you shift the burden of raising a child solely to the individuals who are responsible for the fact that that child exists.
I am a strong advocate for social programs: Single-payer healthcare, welfare programs, low-income housing, etc, but for adults who in turn contribute what they can. A child should only be supported by the individuals who created it.
Net consumption (if I’m understanding your definition here correctly), while important to the economy, gets a little weird when you think about how individual choices impact the overall economy. Technically, if I were to buy less than I’d otherwise use of something, that’d lower GDP (the standard, if very flawed, measurement of economic activity) because I wouldn’t be circulating those funds among other workers. Buying more than I need actual improves the economy right up until the point we run out of the inputs for production. It’s gets more confusing in a service-based economy because service workers don’t technically produce any resources…instead they free up time/energy by doing things for resource producers to make more resources or they aid the process of getting those resources to the folks who want to buy them.
None of that means I disagree with you. From a resource-consumption standpoint, there’s good arguments on both sides of the aisle…each new person DOES use more resources than is sustainable long-term, but we also need enough people to keep the economic engines running smoothly. A big part of why life got harder after the pandemic (and one that doesn’t get talked about much) is that so many workers died or were disabled beyond the ability to work. That’s part of why you see the child labor laws relaxing most in industries that were hit hardest by covid (like factory farming). It’s definitely not always the moral choice to have kids, but to tie it back to OP, the state definitely has an interest in people having the right amount of them.
That all makes sense from an economic/state point of view. From an environmental aspect, 8B is far too many humans for this floating rock. A slowdown in reproduction is a good thing, long term.