Single Option is “necessary” because it is the system that forces everyone to pay the really heavy, middle class destroying taxation, or as it will be termed, “premiums.” It is a scheme for eliminating medical care for non-ruling class retired folks and for immobilizing the population. It also goes far to freezing social mobility as well as geographical mobility. It will resemble in its application the Jizya of Moslem countries used to prevent infidels (in America-middle class folks) from being able to afford to change location or rise economically.
1. They cannot be left to operate under normal economic influences because those influences would likely jeopardize the existence of a nation, state, etc. Military expenditures would fit this description. While the government can open some contracts to competitive bids, it has to operate under a set of parameters -- like government ownership of assets and limits on marketing products to other "customers" -- that you'd never want in almost any other industry sector.
2. They never operated under normal economic influences anyway. Health care is like this. The argument over government control of health care is a pointless one, since individuals voluntarily gave up their right to complain about this sort of thing once they accepted third-party payments as a normal operating environment in the first place. Any industry that is built on third-party payment systems is doomed to fail, regardless of whether the "third party" is a government or an insurance company.