I just figure it's a face saving thing. They figure they can't in one breath claim the bible has all the answers and in the next breath admit there are some things they just don't know. As soon as you claim one book has all the answers of the universe contained within it's pages ( an impossibity) anything not covered in the book has to be either false or not worth knowing in order to maintain your original claim that you have all the answers.
It's becomes frustratingly circular.