An all too common thread between accidents is excess speed.

The influence of road conditions and traffic on what is and isn't a safe speed is way greater on a bike than a car, so even in optimal conditions, where the speed limit was determined for motorcycles, it would have to be understood as a guide of "This is what an average bike could ride with minimal traffic and sunny road conditions, if there's traffic or poor conditions, you should go slower".

consequences for an accident due to the unpredictablity of someone speeding are not shared with society.

True, there aren't zero consequences born by society, but it is far, far less than if you were speeding in a 2 ton steel box designed to protect you at the expense of anyone else, and that should be reflected in the consequences. Same reason I think it's insane that a bicycle DUI in Japan can get you the same consequences as a car DUI, though in practice, cops understand the law is insane and only apply it to foreigners.