Quoting Tarynosaurus Rex:" How is both parents needing to work a feminist issue? That's an economical issue."
Because our definition of "needing" to work has changed dramatically.
I'm not against 2 people working to contribute to the lifestyle they wanted. In the past few decades both parents have usually chosen to work for lifestyle issues AND the fact that women were now empowered to get a better education and job. I think that is a good thing.
What coincided with the feminist movement of the 60s and 70s was "shunning" the traditional roles of women as cook, cleaner and seemstress.