The employer decides what benefits to offer and typically has very little flexibility in how to modify them.
Huh? This is the opposite of the case, IMO.
Employers can decide what benefits they offer, and due to that, they can offer benefits that are really flexible. They can offer weeks and weeks of paid vacation. They can offer work from home. They can offer 4 day weeks. They can offer paid sabbaticals.
They DON'T, because it's not profitable to them, and * you, that's why.
But as we've seen from the FIRE community, once you're valuable enough, and have F U money, it's all negotiable. We have people who have negotiated part time.
Look at RoG's wife:
http://rootofgood.com/first-attempt-early-retirement/Reduced hours, work from home, more pay, and paid sabbatical? That's * incredible.
I don't know how you can say that employers have "little flexibility in how to modify" the benefits they offer. It's all completely flexible.
12 weeks paid maternal/paternal leave might be a great benefit for some but why is it subsidized by everyone?
Since the first two comments were about this, let me clarify before this gets too off track: no one is subsidizing this. In other countries, perhaps. The U.S. does NOT have paid maternity, by law. They have "you can take 12 weeks (unpaid) without being fired". Want longer? Too bad, job can say no.
Some jobs might make it paid, but that would be a benefit they offer, and not "subsidized by everyone."
Your throwing this comment out there about maternity (aside from it being wrong twice, it's not always paid, and it's not subsidized by everyone) will detract from your main post, I fear.
Hopefully this clarification will satisfy everyone, and we can move on to discuss the main point of your post, but knowing the Internet, probably not. :P