I agree that most Christians don't read the Bible, and many aren't even real theists. They go to Church just for the social benefits or because they feel pressured, like Homer Simpson.

But for lots of Christian, just knowing that the Bible exists is enough. Even if they've never read it, the possibility that such a divine life manual exists is enough to take the edge off.

When you start to think there's no such revelation, you see that everything's up in the air, that an asteroid might smack the Earth and no one would come to our rescue because the universe is indifferent to whether we live or die. The chain of existential inferences ramifies.