It's common wisdom that surgeries are better done at high-volume centers. Specialists should do what they're best at - this reduces errors.
By analogy, medical schools should do what they're best at. Different medical schools are (I speculate) better at educating different types of doctors: NYU might be better at training primary care physicians, while Columbia (to pluck a name out of the air) might be better at training future cardiologists.
So why can't medical schools specialize? Why not telescope the long and tiresome haul of medical school-residency-fellowship into a single training program?
We know "physician" is a variegated profession. Why must all doctors be trained the same? Wouldn't it make sense for a medical school to be able to choose an area of specialty, rather than trying (fruitlessly) to be all things to all possible future doctors?