[maxov]

I haven't been a parent so I can't be positive, but I doubt time off for maternity or paternity acts as a "positive" incentive for having children, meaning people who didn't want children before would now want them. That time off is filled pretty well caring for the baby, which is extremely tiring and time-consuming; it doesn't really function as a break. I also don't know how many people would trade a several month absence from work for the at least 18-year (more like lifetime, really) commitment of raising a child; they have children for other reasons.

That said, I could see how having maternity/paternity leave would help people who want to put in the effort of raising children, but cannot/do not want to quit their job or keep working with a baby for the most demanding first few months. There is likely negative pressure on having children from not being able to take paid leave from work, and in aggregate people would probably have more children as a result if they do get paid leave.

Although this is an entirely different topic, such a policy seems like a good idea to combat the lack of births many developed countries are facing, which in the long term will cause an asymmetric demography. This could be a big problem, as countries with births under replacement and little net inward migration need to support an aging population with fewer active workers (see e.g. Japan). I imagine some would argue that we should move toward smaller and more sustainable societies in order to preserve the planet's resources and reduce our total consumption, in which case they would advocate for alternate solutions to deal with societal aging.