Feel free to explain if you think I’m not getting something.
If you think that the SAH spouse’s contribution is always (or in most cases) maximized in the paid workforce, you’re not living in the real world. There are many variables that would make it detrimental to both the family and society, in general.
As recommended to BG, you should read Elizabeth Warren’s book:
We’ve done a lot of damage, in many different ways, by pushing this lifestyle on everyone without taking into account any of the consequences.
Here’s a lecture by Ms. Warren where she discusses some of the issues: