I’ve told him the reason. I suspect that maybe he feels like it’s slightly more difficult to take the scooter back and it’s enough of a hump that he doesn’t do it.
I’ll try setting up a parking area in the back with a place for tools and related things and set it up so that everyone has their own space that they can use and lock up a bike if they have one. I think that giving him his own space like that would be good for encouragement.