Legal Question in Health Care Law in California

Why not?

By making an appointment for patient A, the doctor set aside time that he or she could have spent with patient B, who presumably would have paid for the visit (personally or through insurance). (I am assuming that the doctor had a reasonable appointment cancellation policy that allowed patient A to cancel without charge if done a reasonable amount of time before the appointment, or if the appointment was missed due to circumstances beyond patient A's control.)