I think we need multiple grades of doctor. Even something as simple as being able to stitch up a wound is useful and could lead to positive health outcomes for those who couldn't otherwise afford a trip to the doctor. Better to get some healthcare than have all doctors be the best possible, but inaccessible to the masses.
I'd liken it to gas stations that also have small garages that can change your oil and top off your fluids. You'd probably never want to have them replace your transmission, but oil changes alone are in high enough demand that I'm sure they make up a good portion of all visits to mechanics.
I'm guessing that a similar situation exists with doctors; physicals, vaccines, and a handful of common diseases (like colds) probably make up a sizable percentage of visits. There's a market for someone who can just handle these cases and pass them off to the higher grade doctor when the need arises.
To an extent we have this in the form of various grades of nurses and the dazzling array of specialists that now exist, but it's not quite there yet.