I suppose that there are a number of different categories to deal with, here; there are reasons that are of the type “because bits of it were variously made up to empower the state, man armies, control women, and benefit a priestly class”, and there are reasons of the type “we know from science that Noah’s flood didn’t happen AND we know where the myth came from”… but my favourite reason is “because it’s complete and utter bullshit”. And, of course, there’s the small matter of it contradicting itself…
What’s your favourite reason why the Bible is not a reliable source of information?