Aunt Minnie is in the hospital. Why? — Because she went out and she slipped on the ice and broke her hip.
Why did she slip on the ice? — Ice is slippery. Everybody knows that!
Why is ice slippery? There aren’t many things as slippery as ice. — Because when you stand on it, the pressure melts the ice, a little bit of instantaneous water surface on which you’re slipping.
Why on ice and not on other things? — Because water expands when it freezes, so the pressure tries to undo the expansion and melts it.
The more I ask “why,“ the more interesting it gets!