The market for customers who freely move is very small, as most get their insurance through their employer. Many large companies self fund their own health insurance offerings and just have third party companies administer it.

Everyone else gets stuck with the awful mess of their employer choosing their insurer, switching not more than once a year.

The point is the managed care market is not structurally similar to a utility company. It is only tax rules that disincentivize people from shopping for managed care.

Whereas multiple utilities are disincentivized due to the cost of moving earth and labor to get you the utility.

Also, I like how the trope is managed care organizations wield unlimited power and make enormous sums of money and have laws that help them benefit over everyone else, but their profit margins and stock returns are abysmal.

The employers switch between providers and administrators and negotiate on behalf of the employees on renewals (tweaking plans, threatening to move.) The employers are incentivized because they pay for some of the premiums and to keep employees happy.