I think there's explanatory power in remembering that private, for-profit insurance companies have as their corporate priority maximization of shareholder value. Protecting people from bankruptcy due to medical expenses is not a corporate goal.
If word gets out that a company's insurance is kinda shitty, they're going to find themselves with fewer customers going forward, which is not good for shareholder value. Nickle and diming on a claim isn't where shareholder value comes from, but rather providing a good product that does what it is meant to do.
> corporate priority maximization of shareholder value.
I'm not sure if you're commenting on their observed behavior or their actual obligation. It would be good to put the phrase away since it's usually short-hand for a moral judgement on short-term focus (be sure, I'm not arguing either way here though I do hold an opinion). The fact is there is no legal duty for a corporation to maximize shareholder value, a couple of links:
Attempting to get the ACA repealed by posting lower than average profits (while running less efficiently, not taking all the tax breaks available, and increasing executive compensation and perks) would certainly maximize shareholder value long term.