Mandates mean (almost) everyone you encounter is insured. If everyone has to have coverage, the cost should naturally drop for two reasons: 1) ordinary economies of scale: generally, the more something is produced, the lower the price can be; 2) more people in the risk pool statistically means lower premiums. Left to their own devices, most people wouldn't buy insurance. Self-aware bad drivers are probably the rarest kind (most people think they're above average), and in a completely "free choice" system, the best drivers would likely find themselves victimized by bad drivers who did not have insurance. Costs for the "good" people would increase, as they would be paying both insurance premiums and any costs associated with car repairs and medical bills incurred when irresponsible, uninsured motorists collided with them. Of course, the costs of those uninsured peoples' injuries would also be borne substantially by taxpayers, as injured people receive free charity care that is passed on to others via higher bills and through Medicaid taxes. Mandates work to minimize this unfair cost-shifting from irresponsible to responsible people.