Whatever the motivation, the point of most children's stories is mainly to entertain. A successful story has to be vivid enough to hold a child's attention, as well as get their imagination working. Interesting characters are also important. If a child doesn't find a main character interesting or empathize with them, there's really no point to them reading the story. It has likeable characters, such as Rashid and Mr. Butt and a young hero in Haroun.
Children love when the hero is someone they can relate to.