8 points
The big difference is in stability. Scooters are insanely unstable compared to bikes, for complicated reasons I don’t fully understand, but I think have something to do with where the centre of gravity is, and how the geometry of the forks help force them into self-righting.
The danger scooters provide to their own riders is much higher than bikes. And because of this, I suspect riders are forced to spend a lot more attention on that, which means they have less attention to spare and are more likely to endanger others.