Never having tried this myself, I wonder if it doesn't go both ways. I wonder if women who feel powerless in most other aspects of a relationship (i.e. don't feel like they have much say in the finances, in family policy, etc.) use this as a last resort. The flip-side stereotype is the husband who won't give his stay-at-home wife money because it's "his" and he doesn't want her wasting it on herself. Refusing to clean the house, etc., in retaliation directly affects the kids and would probably bring extra criticism on the woman herself. Withholding sex directly affects mostly the husband.

Which is not to say that I don't think it's a childish ploy and degrading to everyone involved, just that without insight into what drives someone down this road, it's hard to tell what's really going on.