The majority aren't really good at risk calculation, or maths in general, and they see the fact they will have to output money and like to think they will never really get sick. Plus, the current model-- mandating *private* insurance, actually mandates a profit-making private sector (because anything else is socialism), while single-payer actually can be run nonprofit.

Add to that, huge numbers of Americans are paranoid about government (some for religious reasons, did you know Obama is the Anticrhist?), so they assume bureaucrats would just let them die rather than send them for treatment. After all, "If Stephen Hawking lived under the British National Health System, he'd be dead by now."<--True quote from American wingnut who couldn't be bothered to know the location and nationality of his celebrity example.

In short, many Americans are completely ignorant and proud of it.