God is perfect, and since He's perfect, the reason why he must be doing anything must also be for something perfect: Himself. Otherwise, He contradicts Himself in settling for reasons less than perfection.
We might be often caught unaware of this fact, but the other side of our humanity tells us that since we are made from God’s perfection, there would be no higher purpose for doing but also for perfection who is God.
The great picture shows us that God created everything for the progression of His perfection. His creation adds nothing to Himself. It doesn’t make Him any lesser or any better, for the lone fact that He’s God. Since there is nothing and no one more deserving to accept God’s will than Perfection Himself, God doesn’t create because he is egotistic.