I think the key issue is around “abandonment” which requires a bit of “intent”. These guys intend to go and pick these up. The same is true for a car as other pointed out but more importantly when I park my car I intend for it to be where I left it.

“In law, abandonment is the relinquishment, giving up or renunciation of an interest, claim, civil proceedings, appeal, privilege, possession, or right, especially with the intent of never again resuming or reasserting it. Such intentional action may take the form of a discontinuance or a waiver.“

-It would make cool artwork! -I dislike seeing scooters strewn about all over the city.