That's because they negotiated and paid for such a plan.
My sister works for a similar large employer. They hired Cigna as the insurer/benefits administrator, and every interaction is a problem. Your two kids have an ear infection? Cool, we've determined that the second one is due to an auto accident. It's so bad that the company hired another company to argue with Cigna for you.
End of the day, the employer controls the purse, and the insurer is doing what the employer paid for. It's cheaper to hire another company to argue for the folks who have noticed problems than to pay for a level of service.
This option doesn't work because healthcare can't be a free market. Car insurance companies have to compete not only with each other but with alternatives like not owning a car at all. There is no alternative to being alive, so health insurance companies can effortlessly collude to raise prices across the industry knowing that they have the most captive customer base possible.
(b) if we had a reasonable market then some people could have an alternative like paying out of pocket
US healthcare has to compete against cheap healthcare in mexico or whatever
A good first step would be banning price discrimination for medical procedures. Right now you get three different prices for "I pay", "insurance pays", and "insurance denies and I pay". People can't tell you what those prices will be. The whole point of insurance is supposed to be to derisk these kinds of decisions, not increase uncertainty and risk. Attempting to use insurance and getting denied can 10x your cost, so what is the purpose of the insurance?
Stop having employer provided insurance / benefits; just tax and then provide services. No more billing department. Just single payer (we the people) get what a patient needs healthcare.
Otherwise we end up paying more anyway. Someone needs to bail out hospitals.