Theology (or in layman's terms the study of God) is one of the most important pieces of Christianity and everyone in the world has a personal theology.  If someone says there is no God, this is their theology essentially.  For a Christian, their personal theology should be a roadmap for their lives which is why I believe it is so important.  For example,  morally, God is perfect.  He cannot encourage evil nor permit it in His presence (Hab. 1:13).  Part of God’s morality is love, mercy, holiness, peace, righteousness (justice), and jealousy.  Because this is a belief of mine, I am encouraged daily.  If I did not have this belief of God I would probablly be one of the most sorry, worried people on the face of the earth.