What if the government was run like a private insurance company?

We're all familiar with how insurance companies, being smart, will invest a little money as a hedge against a big claim. They'll pay for a free flu shot rather than incur the risk of having to cover the much more expensive treatment of a flu victim. They'll waive the deductible to get your chipped windshield fixed before it turns into a full-on windshield replacement. 

What if the government operated this way? Prime example: we have plenty of evidence that pre-K education pays big dividends in later life, in the form of higher productivity and income, and even better health. It's not even close. If government was run like a private insurer, it would insist on funding preschool because the return on its investment would be so great. 

Some other areas that a rational insurer would want to cover: 

• Climate mitigation and resilience. Much cheaper than ever-increasing expenses for disaster recovery. 
• Clean energy. As has been noted, the health benefits alone would deliver a big payoff for getting rid of fossil fuels. And what rational businessperson wouldn't want to invest in virtually unlimited free energy? 
• Drug development. What if, instead of granting patent monopolies and then struggling to insure the spiraling cost of extortionate drug prices, the government simply invested in drug research and made the results available as cheap generics? The savings to Medicare and Medicaid alone would be massive. 

There are many other areas that a rational private insurer would want to invest in, in order to lower its future payouts and drive down the cost of premiums. But when it comes to government, the anti-tax crusaders view every expenditure on social welfare as a net loss to the economy. Since most of these people claim to be fans of business, how can they oppose the government operating more like a private insurer?