I generally really like keeping safety equipment intact, and using it. So far my record with this tractor is unbroken: every time I have started the engine and every time I have moved the tractor, I've had the seat belt fastened. The only time the engine runs with the seat belt unfastened is if I've parked the machine and am getting off or back on, for example to open/close a gate, or put something into the bucket or take it out, or hook up a chain.
Unfortunately, my seat switch is way too touchy, and I inadvertently shut the motor down numerous times by moving wrong in the seat, such as learning forward a little to reach the 2WD/4WD lever. With the seat belt still fastened, this is.
So I soon gave up, and made a short jumper with spade lugs to short out the wires going to the switch. If I wanted to restore the switch function I'd just have to flip the seat up, unplug the jumper, and push the lugs back onto the switch terminals.
Safety equipment that functions badly gives all safety equipment a bad name, and is part of the reason people are so quick to disable it. And I'm one who could use the extra margin -- I'm definitely not foolproof.