Why do some people never think about god?

There's a number of reasons, but a very common one is that they aren't aware (or paying attention) to their spiritual need. (Matthew 5:3) Others would rather just do things their own way and not answer to anyone, though this won't won't change what'll happen in the future with everyone. (Romans 14:12) There are some that had learned something about God, but due to the hypocrites that taught them & or their lack of understanding of The Bible they turned away from learning any more about Him. Jehovah God did tell Daniel however, that the "true knowledge" (which includes the truth about Him and the Bible in general) would be "abundant" (Daniel 12:4), denoting that it would be easily accessible by most. And, if you look at today's circumstances, that truth is available to a large chunk of the world.

-New World Translation of the Holy Scriptures