Does a Spyder have seat belts to keep you from flying out of the vehicle head first through the windshield? I thought not. Do you wear a seat belt? I would guess probably so (well, maybe not since you don't wear a helmet) . Why not a helmet then? Seems like a no brainier (sorry, bad pun...).
There are seatbelt laws for the exact same reason there are helmet laws. To save lives. To go without either is your choice, but it's a stupid choice, and it's your family and friends that will have to pay the consequences if something happens.
Back in the days without helmet laws here, I lost my father as the result of a head injury that could have been prevented with the use of a helmet. I was only 3, but I still remember the night my mom got that phone call. I wouldn't wish that on anyone. And if preventing that means we have to enact laws so the state has to make that choice for the people who refuse to make the right choice, then so ****ing be it.