Never asked him and I can't recall if he's mentioned it.
The ones who truly see it all, I would guess, have worked in a variety of settings (e.g, inpatient, outpatient, palliative care, rehab), with a variety of client populations (e.g., psychosis, anxiety, insurance paying, cash paying), and a variety of organizations (e.g., private, public).
They would also have a number of years experience. You couldn't have seen it all if you've only been practicing for 2 years or only saw those who could afford to pay high cash rates, right?