The only difference between being a wife and mom is that when you are gainfully employeed by a company you have an instruction manual to go by. The wife/mom has to fly by the seat of her pants; so can't you see why she should be paid more.
I'm a wife/mom/grandmother/great-grandmother and I work full time at our childrens hospital in the IS dept. My youngest daughter and her two kids live with me and on my 3 days a week I get off I watch her kids to save her money. I would't trade it for anything.