This, coupled with insurance companies trying to keep investors happy instead of customers, is the biggest issue with why rates keep going up. They need to turn a profit, or investors will dump them, and with those higher costs involved they raise rates.
I do agree with your comments about un- or under-insured motorists. Those fines need to be more than the 'average' insurance rates of the area/state, to entice people to actually get insurance. And you're right, those of us who are insured are covering those who aren't.
The same happens in health insurance - those of us with it are paying higher premiums to cover those who aren't insured, because if they need a hospital visit or whatever but can't pay for it (they declare bankruptcy or whatever), the provider has to recoup and raises rates, our insurance has to pay more and raises rates on us. Vicious cycle.