The motorcycle comparison is meaningless, because on a bike you are at the mercy of every half blind driver on the road. I've done some 6 figure # of miles on 2 wheels so I know. And I wouldn't ride a bike in the present traffic density.
Whereas in flying some 99% of the risk is down to the pilot.
The size of the residual "1%" or whatever is down to the build quality of the aircraft and its maintenance, and that is also to a large degree under the pilot's control. I know renters get little choice but they can always choose to walk away and rent something better. The best way to get this residual % down is to become an owner, get seriously clued up on maintenance, build a trustworthy team of people you can call on for different jobs, and then you can manage the whole process.
Engine management also comes into it heavily - not taught in the PPL except (usually) to fly full-rich.