A fair number of people do own bikes. But almost certainly the majority of people don't want to own a second vehicle--focused on transportation, rather than recreation--when they need/want a primary, probably ICE, vehicle anyway.

There's billions of motorcycles in the world.

On a motorcycle, I need to wear special clothes and a helmet and it's still rather unsafe.

This thing I just can get in and out like with a car. I can throw my normal backpack in there. I don't need to worry about rain. Very importantly, I at least have some material around me if someone hits me.