Things may be different for your generation. Many are discussing privatizing Social Security and doing away with Medicare. Even Republican voters in the State of Florida are opposed to this plan. Read the report on a survey of Republican Primary Voters who objected 2:1 to plans to change these benefits.
Given what you know of the volatility of the stock markets that are up one day and down drastically another, would you risk your retirement to the stock market? Would you risk your health on having the ability to pay for private health insurance when you retire?