The US is the most pure-capitalist nation on the planet, and medical services are as bad a fit as it gets for a market economy:
* interactions with the market are ideally as few as possible
* there is massive information asymmetry
* people can't "shop around" during medical emergencies
* the externalities are orders of magnitude more potent than the forces directly acting on a transaction
* most importantly, individuals in many cases *literally cannot exit the marketplace* (unless you consider death a viable consumer choice).
That second property creates a market incentive to squeeze every consumer dry. What can they do about it, really?
But it's insanely unethical, and extremely against the common good (externalities abound).
Those forces push the middlemen, the insurance providers, to do horrible shit. And since they are the middlemen with all of the power, and interact with literally every market actor, the culture of pure evil seeps into everything. Clinicians either becomes numb to the fact that insurance companies will literally just not pay things they agreed to pay, or live a life of endless frustration.
This is just "how it is", and so everyone, including regulators, shift their overton window to be able to function in a decrepit, toxic system.