I stumbled upon an article from Ancient Origins and it's really got me thinking. I'm not attesting to the accuracy of everything in this article, but its a very useful tool to get you thinking. Even just the idea of removing books of the Bible to making them more affordable for print and distribution is a very logical and plausible way I could see these books being removed.
There's alot in here, but don't let that scare you away. It's really interesting!