Whenever an appointment is delayed by more than a polite 15 minutes, I inquire about the delay. If there isn't a polite, conciliatory, explanation I leave and seek-out another provider. This applies to every business relationship wherein I'm the client/customer.
Not to do this merely supports a human propensity to forget who is working for whom; who is paying whom for value in return.

One sees this relationship forgotten all too often. Some of the worst offenders are doctors, theatrical agents, union representatives bureaucrats of every stripe. They establish themselves and their roles as 'working for you'. Soon a confusion arises wherein they quickly forget who is subordinate in the relationship. Politicians are the cardinal examples. They beg you to hire them and immedialtely turn their attitude 180 degrees after election to you being their ward...

M.D. after a name doesn't confer privilege or an exalted status. They GET PAID for what they do the same as the gardener. Don't ever let them forget it.