What does the style tell us about the purpose of "The Rocking-Horse Winner"?
In the phraseology of its beginning, its simple style, its direct characterization and its use of the wish-motif--especially that of the wish which is granted only on conditions that nullify its desirability--characterization, setting and ending are especially significant. What do they tell us about the purpose of the story?
The simplistic style of writing, direct characterization and infused moral undertones all make this story a fable of sorts, a tale meant to teach a lesson. It is told simply so that all people can understand it, almost like a children's story. A lot of children's stories out there, fairy tales and the like, have a simplistic tone and style about them, because they are meant to teach a lesson about morals or values. Fables are the same way--exaggerated characters, a simple concept, and at the end, a very important lesson to take away from the story. Lawrence often had a theme to his stories, and in this one it is of greed and how greed is an unmerciful master that takes all in order to exist. It requires sacrifices not worth making, and is never satiated.
The story itself is centered around a child, around potentially magical powers that he has, around flawed and greedy adults, and around a central theme or message, all make the purpose of this story similar to a fable or fairy-tale: to teach a lesson or moral. This particular "fairy tale," however, is quite serious and dramatic, and its ending does not consist of characters living happily ever after. Lawrence paints the picture of a real-life fable, where the real repercussions of flaws are seen, leaving the entire story with a tragic ending to teach the lesson, instead of a cute one-liner like a fable has. I hope that those thoughts helped; good luck!