Simple. Because all evidence suggests otherwise: Your de facto close-mindedness has led to your complaint while Hawking, with his truly open spirit, has successfully looked into the mind of God. Thus he is grateful to have this life to appreciate the grand design of the Universe.
What evidence? There is none. If there was you wouldn't need belief.
Just like I don't believe cats exist, I know they exist.
If you know a god exists, you wouldn't need belief nor faith. You would know.
There is zero evidence for a gods existence. None.
Some people like myself do know that God, Jesus and angels exist.
I've already proven it by showing you photographs of the Holy Spirit.