The public pays for the cost of their injuries, either directly through a state healthcare system or in the form of increased premiums. An insurance company has no way to differentiate reckless motorcyclists who are lucky from responsible motorcyclists.

The cost of the injuries is far less than the same behavior in a car.

A crash on a road will close one or more lanes while emergency services attend the site of the crash, causing congestion

I have only seen this happen once, when a guy did suicide by bike by driving directly into the back of a dump truck doing like 100 on a bridge at 4 AM about a year ago. The bike was ripped in half and the body was so messed up nobody wanted to touch it.

Every other time, someone just walks/drags the bike and rider to the side of the road and helps them get recollected.

Normalising reckless behaviour increases its social acceptability, and I think that as soon as it becomes widely known that you won’t go to jail for operating a motorcycle at double the speed limit, the first people to try this will be teenagers

So by treating the far more dangerous car behavior the same way, are we encouraging people to behave dangerously in cars?

But my point isn't that reckless behavior should be legalized, it's that cases where it's much more dangerous to society should be punished accordingly.

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.

The trauma of witnessing a lethal accident and traffic delays due to cleanup have different severities but each can have lasting impacts on people.

You may not have noticed, but there was no collision in the article being discussed. He was speeding in traffic that was so light that he didn't even need to change lanes. There was no collision. He had something like a 45mph speed differential versus other traffic.

How about you stop pontificating on hypotheticals and look at the actual situation being discussed?

Also, if you're so concerned about the trauma of seeing motorcyclists injured, then you should be focusing on driver training and PSAs about scanning the road for more vulnerable road users. Motorcyclists are injured or killed by inattentive or reckless drivers at a rate vastly higher than the reverse.

500 pounds of bike and rider impacting another vehicle at >100mph can easily kill everyone in that other vehicle.

Maybe if the other vehicle is a tandem bicycle. Nobody is dying in a modern car or SUV due to being rear-ended by a motorcycle with a ~45mph speed differential.

You're not going to be personally harmed under those conditions on a freeway. A side impact due to cross- or turning-traffic on a two-way road? Maybe. Even then, a modern car is going to fare phenomenally well and much of the impact energy is turned into catapulting the rider into the air.

people in cars die to speeding motorcycles every day.

No, they fucking don't. It's phenomenally rare. It's utterly unheard of in one-way, divided traffic.