I have zero desire to be a parent but I think people having kids is a pretty important part of keeping humanity/society going, so I'm happy to accommodate (or even reward) it.
We definitely don’t want to create a situation where parents are less desirable to employ, right?
And, most people have kids (even in places countries with highly developed economies and lower fertility rates). So, we shouldn’t think of this as an extra perk (some special case benefit). The treatment of folks who have had kids is the average case. The special case is whatever we for people who don’t have them (we shouldn’t make a special negative case, right?)
Regarding your second point, I guess you're right. :) I'm just looking at it from my "you couldn't even pay me to have a child" perspective.
Your question about making it a negative case is an interesting can of worms I'll elect not to open.
Everybody says having kids is really rewarding, so the folks who don’t should also get some time to find their own rewards. And, if we’re making extra space for people who have kids, that puts those people at a competitive disadvantage.
I mean, like, we should have maternity leave as a special thing. But everybody should get enough days off to deal with a 10 year old’s baseball games, school plays, doctor appointments, or whatever. And even for maternity leave—maybe just give everybody a sabbatical at some point!