A great many jobs in the real world are learned by this entity called "on the job training", i. e., no amount of formal education prepares you completely for what lies ahead--just ask any doctor about that. In the world of medicine opening up a "practice" means just that, literally. Docs learn as they go along. Heaven help you if you contract a rare disease that a doc never saw before. Referring a patient to a specialist is high on the list of why such a referral occurs, i. e., you're in the realm of "specialized knowledge" that the primary care doc has little experience with/knowledge of.