The oft-stated reason that advocates of the “single-payer” health-care system here (Canada) oppose any supplementary insurance, or direct purchase of health services; is to shore up support for the health care budgets. They reason (probably correctly) that, if people could buy supplementary care, the government health-care budget would be squeezed. That’s why the U.S. is likely headed for a “single-payer” system — which means you will be left with few or no alternatives to the state-run system. (One alternative will be to fly to some foreign country & pay for procedures out-of-pocket. A lot of well-to-do Canadians now travel to the U.S. for faster or better care.)