I raced motocross for Yamaha from the mid to late 70's. I have steel pins and plates in places they don't belong. I have in my trophy case two shattered helmets from crashes in races. I made races enjoyable to watch because I rode with reckless abandon and crashed all too often. Having a seat belt on my motorcycles would not have helped me. Having a full faced helmet on my head saved my life twice. The helmets were designed to absorb the impact and self destruct as they take the energy of the collision. They worked. I'm alive. A motorcycle has no protective devices surrounding it that would afford any benefit to the rider in the event of a crash. The intention is for the rider to be thrown clear. That doesn't always happen, and when it does, sometimes the results are less than ideal.
In a motor vehicle and a tractor, there is specifically designed structural steel to protect the occupant or operator. The design is for the vehicle to absorb the impact, or prevent the vehicle from crushing the operator. For those two simple principles to work, the operator must remain in a known and set position. The seat belt serves that purpose. Without a seat belt, the protection engineered in the vehicle is negated. The operator can easily become crushed, become a missle, or be thrown clear with less than acceptable results.
No preaching here. I'm only stating the facts of engineering and designed purposes. I suppose it is like smoking; it is your choice (except in some states, wearing a seat belt is required). I've often heard my good friends who smoke claim that "you have to die from something". That is true. However, I chose to not die from being crushed by a tractor, becoming a human missle in a vehicle, or from lung cancer. By choice, I'd prefer to die of natural causes at a date in the distant future. Will wearing a seat belt, wearing a helmet, and not smoking assure that? Of course not. It will, however, lessen the odds that I will die or become disabled from one of these specific situations. Life is a game of odds. I simply choose to try to stack those odds as much as I can in my favor.
Your life is run by your choices. I am certainly not someone to tell you how to live your life. I'm only giving my reasons for my answer to your question. Your decisions are yours, and I'm happy with them unless they prevent me from making my decisions as I choose. See, it's really simple. /forums/images/graemlins/cool.gif I will step out on a limb, and say "please do be careful".