Moving in with boyfriend

I am currently a college student and once I graduate me and my boyfriend plan on getting a place together. My mother & grandmother don’t like the idea of moving in with him without being married. They say I’m playing the role of “being a wife” without actually being one. To me it makes sense though because its way cheaper sharing expenses and i know in the future once everything is settled we are going to get married. I need some advice. 🤦🏾‍♀️