It's not like every other kind of insurance, though. Health "insurance" covers many expected and predictable costs, which isn't what insurance is about in any industry.

What we call health "insurance" is really just access to health care with expenses adequately covered, with only the portion of that covering unexpected or unlikely risks properly falling under the heading of insurance.

Additionally, even the true insurance piece is one of the only kinds of insurance where it's a societal imperative (in most people's opinions) for everyone to get the insured benefits they need, regardless of ability to pay. Even car insurance isn't required for people who rely on mass transit.

Health insurance policymaking needs to differ from most other kinds of insurance policymaking for these reasons.

That is an awesome answer, but pedantic. The real question is, again: how do we express the idea to create a REAL market for health "insurance"? It's not about the difference between health "insurance" and other kinds of "insurance." The question is how to express how to create a market for it.

Yeah, I am disagreeing with the choice of a market solution for something which we want to make available to people who can't afford it.

That's not what markets are meant for or good at, especially not the deregulated free market that is often meant by questions like yours. As for a tightly regulated market with lots of requirements about coverage and price, some states already have that, and it's exactly those tightly regulated markets which the "let insurance sell across state lines" proposals want to disrupt.