If you park a car at a random spot it will get towed. Are there really scooter parking spots put up by the city, and are bird paying parking fees?
As I point out in another comment, this is not because being located in a random spot is sufficient to establish that an item is abandoned property. (If it were, the tow truck company would be legally entitled to keep your car!)
Rather, there is legislation which specifically allows towing of cars in certain areas, subject to certain rules. There is no such legislation for scooters.