The problem is minimum standards pose a ridiculously high barrier to entry at some airports. At other airports there are no barriers. Add to the mix are established flight schools using minimum standards to protect their turf as
@write-stuff described above.
Sometimes there are Barney Fife airport managers and busy body tennants who try to insert themselves into independent CFIs providing flight training. For example, I know of a nearby airport that will not allow a CFI to brief or debrief a training flight in the pilot lounge even when the client is an airport tennant airplane owner. That might or might not be a problem depending on one's temperament.
As you keep pointing out, there's nothing illegal about having high standards. If the city or airport sponsor wants Gucci flight schools then that's what they get.
I know the mayor of our city was super impressed by the "free" cookies at a Signature/Atlantic or some other big FBO chain he passed through and now that's what he wants for his city instead of the city running the airport. It won't be good for the rank and file small GA airplane owners. You can be sure his experience will be a part of minimum standards someday.
The only recourse is to get the standards changed or find an airport to operate out of with lower minimum standards.