Why do Christians say that it is not important to know who wrote the Bible?

Well Christians say that because Paul (who never met Jesus) wrote that all scripture is inspired by God. I personally think it's very important to know who wrote each book, because they might have had their own agenda separate from God's. Like, for instance, Paul. Paul really wanted to get to see Jesus in his lifetime, so he preached that everyone should refrain from having sex so humanity would die out and Jesus would be forced to return.