Because your brain likes questions and your brain thinks it exists. The world neither exists or non-exists, it just is , and has allowed the evolution of brains that ask invalid questions such as what is its origin and purpose. Origin and purpose are useful concepts to avoid dying when an arrow comes from an origin and aims to kill you. Our organic neural networks have a tendency to apply these concepts to everything, that's sometimes vaguely useful, other times it's just brain farts.