I don’t think anyone is incentivized to have a kid because they get a few weeks or months off. The only incentive i see is the opposite; if there is no parental leave, they may decide not to have children they were otherwise considering.

And the few weeks/months after a child is born can be much harder work than your day job in many aspects. So it would be unfair to parents, especially mothers, who tend to spend more time on child care, to force them to use their sabbatical/vacation time as parental leave. You’d effectively be controlling people’s reproductive timelines with this sabbatical schedule.

In terms of women being disadvantaged, I agree. But I think the answer is to make sure it’s illegal to discriminate based on current or future parental obligations and enforce that strongly, and to strongly incentivize both mothers and fathers to take their full allocated leave, and make it the same length for both parents.