This article goes over some of the benefits of having a medical marijuana recommendation (MMR). https://www.hellomd.com/health-wellness/5a302030100a820006562ebf/why-youll-still-need-a-medical-recommendation-after-jan-1
I know from some news sources (SF Chronicle) that some dispensaries are requiring a state card along with an MMR. They are doing this as a precaution. It’s not required by law that everyone have a state card but there’s a lot of confusion, even among dispensary owners. If you have an MMR and don’t want to get a state card, I’d call dispensaries before I go to see what they are checking for.