While the overall ration might not be terribly high, one can read again and again about cases where Apple did reject apps or app updates out of the blue. Some got resolved later on, others not. A common theme is, that you don't really have a direct point of contact, you can only send appeals to Apple. And when they decide to block you, you are done. There is no alternative. I wonder why lawmakers have not dealt with this topic yet, but alternative app stores would go quite a way of reducing the problem.