Tyler Cowen explains it all

Best paragraph I've read all year:

Government-dominated health systems, insofar as they work well (a number of them do), succeed simply by lowering costs. Health care has a murky relationship to human health, pharmaceuticals and broken limbs aside. A version of the single-payer system, as might be adopted in the United States, would not lower costs. We would be raising taxes and lowering medical innovation to give poor people a good deal more financial security and a slight bit more health; that is the relevant trade-off.

This is part of the year's best blog post, so you should go read the whole thing.