It means that folks won't lose their job when the doctor orders bed rest in the last month. It gives time for proper care of children. And so on. You might be helping pay for someone else's benefits, but if you ever need them, you are paying for your own as well.
Heck, I'm childless by choice (and female on top of this) and I completely approve of such things - for both mothers and fathers. I'm fine with parents getting more sick leave for their children. After all, they have more responsibility than I do. Children with proper support are more likely to grow up to be good adults. I will probably need these adults as I age.
And it isn't like this sort of cost is limited to such things as parental leave. If you pay for your hospital bill, you are helping pay for folks that do not. Shop retail? You are paying for theft, charity work they do, and whatever benefits they give their employees. Pay taxes? You are helping pay for roads you don't use, wars you don't agree with, politician benefits and pay, and a slew of other things.
I'll add that sometimes the placement of price makes all the difference. For example, when taxes are included in the price on the shelf, there is no more pain at the register. Most places have electronic receipts that can tell you how much tax you've paid, so the cost isn't hidden. Taxpayer-funded health care means you can better budget for everyday life's ups and downs, especially the health things that are out of one's control. It matters where the price and cost actually are.
There's a societal cost to not paying for rational breaks. You get breakdowns instead.