Husband trooning out actively harms her. She loses all the benefits a man brings, from protector, to attraction, to even monetary. They can pretend otherwise but every woman knows these things and their value subconsciously.

A trooned kid is all benefits. She gets accolades, social clout, and constant nut fluffing. It brings no negatives to the mother herself. Sure they might suffer and all that, but that's even more free attention and victimhood for her.