“Mind you, there are thousands of clever men who would give anything for the chance to come in and take over from me, but I don't want that sort of person. I don't want a grown-up person at all. A grown-up won't listen to me; he won't learn. He will try to do things his own way and not mine. So I have to have a child.”

In the last chapter of the book, Mr. Wonka explains to Charlie his motivation for sending out the golden tickets. He knows there is any number of adults who would be willing to take over the helm of his factory. But if Mr. Wonka chooses an adult successor, he will worry that they will change everything about his beloved operation. He needs someone who will listen to everything he says and who will do everything according to his precise wishes. Only a dutiful and respectful child will fit the bill for Mr. Wonka.