As a lawyer I'm sure I have a skewed view of insurance companies, but IN MY OPINION they do in fact push legislation to keep medical costs down, but only so they can continue to maximize profits. If your state is a "no helmet" state (like my state), and tomorrow they enact a helmet law, will your policy rates go down? I guarantee you the answer is "No."
Cars are much safer now than they used to be. Why? The new ones crumple up like a wet paper bag in any accident. A minor "fender bender" now will cause $8,000 damage to a new Accord/Camry/etc. It does work, but the expense is incredible. Now combine all those "fender bender" repair costs to the overall medical expense for the occasional motorcycle wreck w/a rider w/gear vs. w/o gear... The "you not wearing gear makes MY insurance go up" argument IN MY OPINION doesn't fly.
Our insurance will always go up, no matter how much gear we all wear or not; helmet laws or not.