Why do you think that is?
I think in relationship to high performance cars and motorcycles, it's the age group that are attracted to them, and the usual inexperience that accompanies that young age.
High performance, 1 liter sport bikes today are capable of extremely high speeds. (180+ MPH right off the showroom floor). They attract young inexperienced riders, who then proceed to ride them far beyond their skill levels, and end up crashing. Many times due to showing off, peer pressure from young women, etc.
Where as Harleys, Gold Wings, and other "cruiser" type bikes attract older, more conservative riders. And many of them have far more years, and much more experience riding motorcycles. That equates to fewer accidents.
These high performance cars are much the same. Years back it was very difficult, if not impossible for young people to get financing and insurance for these type of cars. Which helped in keeping them out of their hands.
Today it's easier than ever to borrow money. So again, these cars end up in young, inexperienced drivers hands. The result are a lot of totaled vehicles, along with the injuries and death that accompany those type of serious, high speed accidents.
And even in the high cost "Supercar" realm, there still are a lot of older people with more money than brains or skill. Hence more wrecks. They just end up costing more to fix..... Assuming they're not totalled.
Just look at how these predominantly young people drive at these insane, "street takeovers". People getting hit. Drive trains blown up. People smashing into each other..... All driving beautiful, expensive high performance cars, that are anything but paid for.
All of this adds up to a much greater chance of a disastrous outcome.