The doctor writes the prescription because if he/she doesn't you go to another doctor who will. They don't want to lose your business and are willing to write a

The doctor writes the prescription because if he/she doesn't you go to another doctor who will. They don't want to lose your business and are willing to write a prescription to make you happy. If all the doctors agreed to not write unnecessary prescriptions you wouldn't have this problem but that's unlikely to happen since only a few doctors will deviate to get the extra patients.