As far as I'm aware, your parent's question is fundamentally in error -- the legal reason you can't take Bird's scooter is that it belongs to Bird. This is the same reason you can't take anything else; there's no conceptual difference.
Whereas with cars, there is a special legal difference which allows tow trucks to confiscate random people's cars even though the cars are neither the property of the tow truck owner nor abandoned. Cars do not enjoy any special privileges. They are the subject of a special legal burden.
To take possession of a Bird scooter, you'd first need to establish that it was abandoned property, which seems like it would be difficult to do. But maybe it's easy! Consult your local law of abandoned property.
Whereas with cars, there is a special legal difference which allows tow trucks to confiscate random people's cars even though the cars are neither the property of the tow truck owner nor abandoned. Cars do not enjoy any special privileges. They are the subject of a special legal burden.
To take possession of a Bird scooter, you'd first need to establish that it was abandoned property, which seems like it would be difficult to do. But maybe it's easy! Consult your local law of abandoned property.