Your question makes it sound like he's stealing from someone by taking paid time off to be with his child. In reality, the money is coming from a corporation, who presumably has already costed the risk and is willing to accept it.

Moreover money is not zero-sum. The way you talk about it, there's only a finite number of dollars in the US and he's stealing some from someone else. This is not even remotely how our economy works. And frankly that's a crazy idea that could be applied to all kinds of things. For example, by working you're stealing money from your employer who could easily spend that money on himself. How dare you work?

In my case, I get a paycheck from my employer as usual. I'm not sure how the specifics work; my employer might pay a premium to a private insurance firm and receive reimbursement from the firm when employees go out on leave so that they're not paying salaries of people who aren't working for them. But at any rate, the cost of providing this leave is similar to other non-mandatory benefits provided by a company (like health insurance), which gets rolled into the cost of doing business and likely gets passed on to our customers.

My wife's leave comes from our state's short-term disability insurance program, which I believe draws its funds from state taxes.