Nobody told Humana they had to be in every market.
There are a multiplicity of regional differences and markets. New England has fishermen who have one life/health-risk profile, while eastern Tennessee and Kentucky and other coal-mining regions have another set of needs and realities entirely. Then there's uranium miners in New Mexico and offshore oil workers in the Gulf of Mexico.
"One size fits all" is, to coin a term, cultural imperialism -- and bad market research.
Then there's federalism. The Civil War didn't abolish States, and States are still the repositories of the People's original sovereignty, and the guarantors of our liberty to a degree often not appreciated.
And there shouldn't be anything stopping the insurance companies from charging more to higher-risk groups for coverage. What's your point?
Are you arguing that higher-risk groups should get less health care?
Having a standard that works across all states allows for cross-shopping by customers. That is increased competition, which leads to reduced costs.
Also, the larger the market... the more the insurance companies can spread the risk. Which is how insurance works, using the premiums paid by the health to pay for the medical care of the sick. And a 300 million man market spreads that out over far more people than a market of... let's say, San Francisco (which has it's own separate medical insurance market) alone.
And that *ALSO* reduces the costs of insurance.