Ours had a small office a few blocks away.

It's actually Medicare and stark law that killed that practice.

Basically, if a doctor collects even a single dollar of Medicare, they're bound by stark law in all contexts. Stark law has very strict rules and penalties for self-referrals, which can include simply sending a patient to your own nurse for a test. There are exemption for self-referrals in medical groups.

So basically, stark made the regulatory risk of private practice too high and legally complicated, so doctors formed medical groups. Those medical groups got bought up.... wash, rinse, repeat and now you have monsters like kaiser.

Don't ask me about how this changed malpractice and basically insulated doctors from a lot of liability (Kaiser kills people. It's a built in cost).