Can a society really be called free when the majority can impose whatever it wants on others? Democracy is not equal to freedom, and a dictatorship by majority rule is not only possible but likely in the absense of constraints.
Ultimately, it is an individual choice. People choose to wear a helmet or not based on a personal cost-benefit analysis. In my case, the answer is: usually, a helmet is warranted. Sometimes, I choose to leave it at home. My head, my decision.
For the person who pointed out that insurance holders pay for coverage-not quite. Insurance companies make money off of investments. The premiums provide the investment capital, and claims are paid from a pool of operating income. Even if you were correct about the workings of the insurance industry, your reasoning opens the door to some disturbing possibilities. I personally don't want the government or the insurance company to come to my home like OSHA without a jockstrap, performing actuarial analysis on the personal minutiea of my life.