Why was this woman in the habit of never referring patients to specialty care practitioners? Recently, I was able to take the time to watch each episode of the series and I have thoughts on it. As a series, it was a giant of its time. In the 1990s like most people then, I watched the show up until the 3rd season and that's about all. Now that I have watched the show in its entirety, I see the cracks between the actors and their story-lines on the show.
To begin with we have to address what happened with Colleen. She's a broad blonde teen in season 3 and in season 4 she is a toothy redhead. To make a plot around what happened to the original Colleen (if you didn't know the real story is a contract negotiation breakdown according to Wikipedia), we could build a fan theory that's ridiculous, and here it is.
Colleen part 1 was killed off for knowing too much and Colleen part 2 eagerly took her place. The show has the other characters believe that "Dr. Mike" is a polished, ahead of her time female doctor. What if instead, Dr. Mike was a midwife or nurse with a lot of ambition, who moved west to start her own practice after stealing her father's library books, him being an actual doctor? It explains why Dr. Mike didn't stay in Boston (her home) and why she choose the middle of nowhere to set up shop.
If Colleen part 1 was in on the whole secret and was learning to be the next faux diploma doctor she would have had some leverage over her mentor. In the interest of keeping her secret, Dr. Mike might have murdered Colleen part 1 and replaced her with a fellow medical hopeful. The brothers might have gone along with this because they might have been getting paid off, threatened or both by Dr. Mike. After all, who would mess with a woman who has an armed enforcer (Sully) and connections with an intimidating pimp (Hank)?
The town would go along with Dr. Quinn's sham on account of her being a better medical care provider than her competitor Jake. A plus also being that with her someone could help birth the brothel's babies and send them off somewhere quietly (...or bury them in a backyard). Most of the town was safe from Dr. Quinn's wrath unless they were females of childbearing age, rip Ingrid.
Of course, this is all fun speculation, a theory for another day is that Sully was a hallucination and Dr. Quinn was an escaped prostitute. Maybe I'm just excited because there are talks of a series reboot and my nostalgia now feels like it's getting a warm hug. BTW Jane Seymour is the queen of the family values drama genre.