I use "why" a lot. For example:
Me: Well, there's this couple and they move to take up a new job in the country.
Inner three-year-old: Why?
Me: Because they want to bring their baby up in a clean and healthy environment.
Me: And the neighbouring farmer wants to sell the magic mountain and move it off his land.
And then I have to think up a plausible reason and then I also have to think up interesting ways of showing the answers to the ITYO's questions rather than just explaining them in the narrative.