I stayed at home to look after the DC, because we thought that one of us should and where we live there wasn't a job for me, but DH had one which could support us all. He had to work up to 90 hours some weeks, so he needed someone at home almost as much as the children did.
I have always found it annoying when people talk about non-working mothers, meaning those who are at home with children. As Pepper59 says, you are on call all the time - 168 hours a week for a breast-feeding mother - and as she also points out, either you pay your salary to child care, or you just do without it while you are at home, so it comes to the same thing. In the meantime, you are working hard, but not for money. When you go out to work, you get paid for it, that's all.