Why do scientists do this?

Why do they want evidence, have the Bible, deny it, and try to come up with their own evidence?
Update: If you think about it, wouldn't you be pretty pissed if 5000 years from now, people find our history textbooks and think it's a bunch of crap?
Update 2: And people actually saw a person make the books of today so you can't use Harry Potter and the 3 Little Pigs as an example.
21 answers 21