It is a simple scheme

Most of us who have had group health insurance plans have dealt with "provider networks".  By going in network, you get a better benefit from your insurance carrier.  As an example, one plan I used to belong to would pay 90% of the "usual and customary rate" (UCR) for a medical service/procedure if you saw a doctor in their preferred provider network, but only 70% of the UCR when you go to an out of network doctor.  Better still, the doctors in the network have signed a contract to accept that 90% reimbursement and your required co-payment as payment in full.

Example:  You have an abcessed thigh.  The procedure to repair it is done and the doctor bills the insurer $300.  The contracted rate is $250.  The doctor gets $225 from the insurer and $25 from you and has to write off the other $50 part of the charge.  If you go out of network, there is no such limitation.

Now what insurers are doing is shrinking the pool of preferred providers by refusing admittance to their networks when doctors try to join.  Especially doctors who often argue claim denials, and work to get their patients the best possible care, even if it means the insurer has to spend more money that it would like. 

Example:  A doctor sends in a request to get authorization to have a patient undergo a scan for coronary artery disease.  The patient doesn't show enough risk factors for the condition and the insurer denies the request.  The type of doctor these networks don't want is one who will take that denial, appeal it and provide more documentation that shows there is a medical necessity to do the test.

Why would these insurers do this?  Because they can negotiate lower rates of reimbursement with the smaller pool of providers, who get a much higher patient volume in return.  The people covered by the plan don't like it, but most will switch doctors and get more coverage rather than accept the higher out of pocket cost of keeping their doctor who is no longer in the network.

There was a trial recently involving a doctor from the Porter Ranch area who sued Anthem Blue Cross for just such an instance and he won.  This is a good thing.  Doctors need to be able to advocate for patients without worrying that the networks they belong to, which provide them with a stream of patients to care for, will drop them.

There are those who say the profit motive and the laws of economics should be allowed to govern healthcare.  Think about this for a moment.  I can shop around to buy a new car and get the best deal.  I can shop around and get the best deal for car insurance.  But I can't possibly shop around to find out which doctor will give me the best deal involving the cost of repairing an abcess on my thigh.  It just isn't comparable.  Should a person having a heart attack be rushed to the closest emergency room, or the one that's in their network but happens to be five miles further down the road?

I'm a big advocate of not forcing health insurance companies to insure "known risks" without a way to fairly compensate them for doing so.  It isn't right for a person with a chronic condition that costs tens of thousands of dollars monthly for treatment, with no outcome that will fix the problem or reduce the costs anytime soon; to be able to pay the same premiums as a completely healthy person, if the condition was known at the time the policy was sold.  I've yet to hear anyone offer an argument in favor of this that makes sense, with the sole exception of everyone getting coverage in the same plan so that we're pooling all risks among all of the people in the pool.