Emergency care, yes, that's unpredictable, and that's the sort of thing that health insurance should cover.
End of life care is not always unpredictable. In fact it rarely is in terms of the general need. Yes, you can't predict the exact point in time at which an 80-year-old person, say, will have an event that makes them require assisted living or a nursing home, but you can certainly foresee well in advance that such a need will arise at some point around that age. So this is not an unexpected need in the sense that emergency care is. And there's no reason why the same health plan should have to cover both needs, yet that is what the US health system does.
> you can't leave in practice even if its theoretically legally possible
Yes, this example of yours is an case of an unexpected need that health insurance should cover. However, I don't know of any "health insurance" in the US that only covers cases of unexpected need like this, and does not also cover everything else that is in any way involved with health care.