All quite rational, and irrelevant to my preceding point...
Insurance coverage for well-care is an asinine idea as well, but also outside this scope.
My question was, “who stops the market from absorbing these risks and costs, absent government regulation?”
Nobody stops the market from doing anything, except that the entire system collapses because nobody can afford an insurance policy when the market prices these risks accordingly.
Government intervention is what happens under public pressure when the public realizes they can't afford something they think they're entitled to.