Medical Assistants are specifically trained to work in physician's offices. That's why they are preferred for that role. They learn things like basic lab testing, phlebotomy, how to set up procedure trays, how to assist with routine procedures, sterilization of instruments, etc. that I know I didn't get in nursing school. They probably don't get paid as well because they don't work pm's, nights, weekends, or holidays like nurses do. They also never need to make independent nursing decisions because there is always a doctor present.