That's what insurance is for. When you buy insurance you're making an agreement to socialize risk, so you're never faced with a $1M bill to save your life.
Even without underwriting it's still insurance, which is "a practice or arrangement by which a company or government agency provides a guarantee of compensation for specified loss, damage, illness, or death in return for payment of a premium" according to Google's dictionary.
If there was a soup kitchen that charged something, maybe on a sliding scale, but not nearly enough to cover costs, it would meat the dictionary definition of a "restaurant". Calling it that would nonetheless be misleading.
Yes but in this case, virtually everyone agrees with the precise dictionary definition of insurance and uses it in daily conversation all the time. Very few would agree with you that health insurance without underwriting should not be called insurance. Political discourse, everyday conversation, and the law itself still call it insurance.
(And while I don't think you meant the comparison this literally, I'll point out that health insurance companies do cover their costs. In fact, they're generally quite profitable.)
Why would it cost $1M for everyone? Not everyone has a disease or an accident. And if we were all greatly diseased at the same time, the price tag would be the least of our worry.
Insurance is paying small sums, at EV negative cost, to mitigate the risk from a rare but very expensive cost.
Health insurance isn’t underwritten and pays out for routine expenses. It isn’t insurance.