Governments have dual interests - have better benefit:cost ratio and spend less tax. They are oversighted by quangos and tax-payers.
But a more interesting question is why people don't help themselves - we know about the importance of good food and exercise and sensible drinking and not smoking and not driving like an idiot etc, yet a lot of illness is caused by entirely preventable stuff.
We know that even if people can get medication they don't take it properly. (There's no difference between the UK (where most people getting meds don't have to pay for them) or the US (where most people have to pay) or the severity of the illness (most transplanted organ failures are because people don't comply with the medication regime.)
This is a significant cost. Just the cost of the meds - in the UK we spend about £9billion per year on meds, of which about half (£4.5billion) is wasted because people don't comply with the instructions. And then there's the additional cost of treating those people.
How would an insurance company get customers, if their services aren't good for customers?
And the only time you know your insurance is lousy is when you're trying to make a claim - at that point you may have years of time with and payments to that company.