Some do, they're called HMO's (Health Management Organizations), Kaiser Permanente being a prominent one. A lot of people don't like having to see a doctor not part of the organization without going through headaches, however, which lead to the prevalence of modern PPO's.
> Some do, they're called HMO's (Health Management Organizations), Kaiser Permanente being a prominent one.
KP is an HMO, and does own its provider network rather than contracting with providers (for most things, at least), but that's not a defining characteristic of HMOs. Many HMOs have contracted, rather than insurer-owned, provider networks.
But the issue is still the same: the network of doctors you can see is very much restricted. And in any event, the way Kaiser is structured (at least in Southern California, where a friend is a Kaiser doctor), the doctors are employed by separate legal entities which contract with the hospitals. So it's kind of a distinction without a difference. HMO implies vertical integration where incentives line-up differently than when providers and insurers are more at arms length.
That said, PPOs also have in-network restrictions. They're looser, but PPOs are also often significantly more expensive.
In my limited experience, it's not the network restrictions per se, but that people want to continue going to a specific doctor or to a specific hospital. My relative who is a partner at a law firm rails against Obamacare because of the ridiculous premiums her firm has to pay. But they only pay those premiums because she demanded a policy that allowed her to continue seeing the same doctor she's seen for over 20 years. She's smart and almost always votes Democratic; the cognitive dissonance in her rants would be comical if it weren't for the fact that so many people exhibit that kind of thinking.
I use Northern California Kaiser and love it. For one thing, it's ridiculously inexpensive, all things considered. And I don't expect the kind of relationship with my doctor portrayed on television. Kaiser is very technologically savvy and data driven. (Though that doesn't mean they used the latest & greatest tech). Their doctors are disciplined to attend to patients efficiently. I've never felt rushed or anything of the sort (even during the 48 hour birth of my son), but neither the doctors nor staff will linger unnecessarily.
But because Kaiser works as a holistic entity, some people may feel neglected. Kaiser dis-intermediates you from the doctor and his personal staff. Appointments are booked on the web or via a call center. For illnesses, you first contact the Kaiser nursing call center, where a nurse and on-call doctor will do a preliminary diagnosis over the phone and often even write a prescription. For common injuries like sprains, etc, you might be scheduled to see a doctor at their sports injury center or similar specialized department, which at my medical center is conveniently (and I doubt coincidentally) located across the corridor from the imaging department. Follow-ups with a doctor will often use their electronic messaging system (basically, web mail).
I _love_ that aspect of Kaiser because I appreciate the effort that goes into reducing costs and improving outcomes. For people who want to feel coddled by their doctor and his staff, or use them as an outlet for their anxiety, it's probably a nightmare.