Why is being a stay at home mom looked down upon?

ok so basically I was talking to my friend who's pregnant and we were talking about how she would handle having a career when her child is born and she said that the childs grandmother (her boyfriends mom) was going to help them out with taking care of the baby and then she asked me what I was going to do when/if I ever had children and I told her that I would most likely quit my job or if we couldn't afford that then just work part time because I wanted to raise my kids myself and not have my mother in law or my mother do it for me ( not that there's anything wrong with that..) when I told her that she said that it was stupid to do that and that I've worked hard for my career so why would I throw it away, also later that day when my boyfriend came home and asked me to make him something to eat, I did and she gave me a weird look and said people like me were the reason why " girls are looked down upon" so basically is she a bitch or am I stereotyping myself?
Why is being a stay at home mom looked down upon?
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