For most people who get sick, the illness is, as we say in RI, fate-appointed not self-appointed. Since most illnesses are fate-appointed rather than self-appointed, it is ridiculous to expect the ill to provide for the cost of the care they need.
Sometimes, for example with smoking, a behavior leads to an illness. Here the cost of the treatment could be covered by taxing the source of the cause of the illness. These illnesses are then economic externalities.
One thing I noticed when thinking about health insurance, those costs that are payed by the government out of taxes (not including taxes to pay for health care externalities) are disproportionately paid by the wealthy. For costs paid by insurance companies, those insured pay the costs. That would explain why the wealthy are so against the government providing health care.