Moreover, an employer is 'selling' their reputation to potential talent as well as selling their product.
Perhaps I'm not working for companies who are as ruthless as you and the other commenter, but as my previous comments alluded to, I actually have updated my CV, and left jobs for other, better jobs, mostly because there was a work-life balance improvement to be gained from the move. And yes, the work-life balance improvement in all situations was a more accepting and flexible remote-work policy. And that was after using available avenues (asking manager(s), 1-1s, etc) to see if a WFH arrangement was viable.
In all cases, I did so with tact and professionalism.
That might be getting lost in translation, because your comment seems to indicate that I just walked into my bosses office and complained that my life sucks and I need to work from home, or else. And that I should be given a handout.
In my opinion, you use what avenues are available to you to see if WFH is possible. If it's important to you, and you aren't getting met half-way, then it's time to start looking elsewhere.
First, your quality of life isn't really a selling point from employers point of view. To raise your odds at negotiations you should focus solely on the employers problems. The same applies when selling something - you should not focus on the benefits that you as a seller get (like money), but on the problems that get solved from the employer.
Secondly, focusing on raw productivity on alone seems to be quite a common thing on these discussions. I think it is quite limited viewpoint, since a ton of other things matter as well in addition to productivity. Communication with others, spreading your knowledge, trust issues, where to focus, etc.