Cancer treatment to this day is not magic, it's not like taking a pill other than in extremely rare cases. You should spend time looking at cancer statistics, the oft mentioned statistics state death rates are a result of "cancer or cancer treatments" because the treatments take a toll on your body and leave you disabled or infirmed for the rest of your life. Until we have better treatments, which are coming, yes if a tumor will go away on its own you best believe it this is better for the quality of life for patients. In fact, the people who stand to lose the most from such a re-diagnosis would be drug manufacturers or even hospitals who can charge a lot for radical surgery and hospices who care for patients undergoing chemo.
(Ideally, as a customer you'd have a choice between plans that do and do not cover a particular treatment.)
They have maximum profit rates, as a percentage of revenue. So the two ways to grow the revenue, and therefore profit, are to 1) capture a larger percentage of patients, and 2) make sure that all patients, including competitors, start using more expensive care options all together.
System-wide cost savings do not increase insurance company profits. This could be considered a good thing or a bad thing, depending on your point of view, I guess.
I had always considered it a bad thing, but given the thrust of your comment, perhaps it's good that there's no incentive for health care companies to push cost-savings measures as an industry.
For the government the only thing that matters is net tax revenue. Healthy people pay more taxes and unhealthy people cost money.
So the solution is obvious: invest in effective low cost preventative treatments and cures. That maximizes net tax revenue.
Meanwhile private insurers only care about your health to the extent that they get paid. Healthy people bring in less money than the chronically ill.
Cost is a big factor in which one you go with. So while insurers do make more money by paying higher and more claims, that’s offset by customers wanting a low price.
[1] https://www.ama-assn.org/delivering-care/patient-support-adv...
[2] https://www.ama-assn.org/delivering-care/patient-support-adv...
Individual companies wanting particular things covered is quite different. And the topic of this thread is why is the entire field shifting in their care in terms of what's thought to be medically best.