I imagine it's unlikely the doctor's office "messed up the timing" such that the doctor isn't doing work and simply making you wait for funsies, but rather the patient before you needed an unanticipated amount of extra time for one thing or another. This is "acceptable" to the business as the doctor is still performing a billable service. It's not preferable, as it would be better if the doctor was performing MORE billable services per day, but acceptable. In hospitals, the number of services performed per day can be used as a KPI, for example. It's "unacceptable" to have the doctor waiting around not performing billable services as that doesn't make money.

If they're messing up the schedule in a way that you both have to wait and no one is performing a billable service, something has seriously gone wrong.