Health insurance in the United States is a shit show. The Medicare for all that Bernie is proposing is a reaction to the inability of Congress to meaningfully fix the issue. I personally would prefer a market based approach to fixing the issues with obtaining medical care, but Congress can't do anything because there's just too much money and influence involved.
Italy has a thriving market based private health care industry. You can call in and get prices and everything. Just that it's in addition to the single payer system, which means the private one is cheap because the competition is 'free'. As a % of GDP, Italy spends a lot less than the US in health care, and people live long and productive lives. I mention Italy because 1) I lived there and 2) it's not some perfectly…
government entities can get subsumed by politics and bureaucracy, while private markets can get distorted by poor regulations and anti-competitive practices. if bureaucrats can get thrown out for not being competitive with the private companies, and private companies can go out of business for not being efficient and serving customers well, we might get decent service-oriented entities in the market.
many goods that don't fit the simple paradigm of commerce (e.g., housing) can benefit from such a model.