Why? It's not rocket science, and it's not like this is a complex decision that you couldn't adequately make after 15 of Internet searching.
The fake mystique imparted on general practitioner doctors is a toxic force for bad in the world.
> Doctors shouldn't be prescribing antibiotics unless there is a big real need.
The doctor doesn't know if there is a "big real need", and in fact cannot.
The doctor is just running off a standard checklist for one of among 50 almost exactly alike cases during his workday.