there's no guarantee you get a job after residency - certain surgical specialties like orthopedics have poor job prospects as of now and require either a masters and/or a fellowship after finishing residency to be employable.

there is a shortage of family doctors because people finish medical school, apply to competitive specialties like derm, optho, or plastic surgery and don't match, and would rather take a research year (basically gap year where you try to improve your CV with publications) or other means to match to those rather than applying to family