Why can’t doctors treat family members outside of emergencies?

Last week, the Medical Board of Australia issued a stern reminder to doctors not to treat their family and friends, warning it was not “good practice” and “fraught with problems”.
Based on my own experiences, I would argue that this dictum must be flexible.
My father, at 60, collapsed at home after being told by his doctor that his chest pain was “only muscular” — despite also experiencing heavy sweating and loss of consciousness.
My mother called an ambulance but was told there would be a 5-6 hour wait.