Here is a excerpt from Sinclair Ferguson on why people reject God. I recommend his book "A Heart for God" if you have not read it.
The fact of God's eternal being makes its impact in different ways. For the unbeliever, it is absolutley intolerable. It tells him, 'God is God; you are but one of his creatures. Your only joy is to be found in obeying him, your true fulfilment is to be found in worshipping him, your only wisdom is to be found in trusting and knowing him.' As Augustine so well said, the heart of the unbeliever will be restless until it finds its rest in God.
These Facts are the ultimate threat to the independence, self-centredness, and sinfulness of the unbelieving man. Of course he says that he has 'intellectual difficulties' that make the God of the Christian faith unacceptable to him. But no man or woman ever rejected the gospel on intellectual grounds alone. The ultimate grounds are always moral. The philosopher Nietzche spoke frankly when he said, 'If there is a God, how can I bear not to be God?' That is the real truth about man: he wants to be his own god. He cannot tolerate that Another is God. So he exchanges the truth about God for a lie, and worship and serves something in creation (his house, his car, his family, his sporting interests, money) rather than the Great Creator of all things (Rom 1:21-21)
- Sinclair Ferguson from A Heart For God