The use of rhetorical questions help the speaker develop their ideas by putting emphasis on their points. If you listened to a speech or read an article on something like, let's say, banana prices and they said something like,"Do you want to go to the store and get those bananas at a decent price? Do you want to be able to share this experience with your friends and family? Do you want your children to taste bananas?" Then that would be a good use of rhetorical questions to push forward their ideas.