I'm new to this forum and decided I'd contribute something silly as my first post.
So remember how Gandalf was speaking so intently about how they needed a burglar and that Bilbo was a good candidate?
To me it sounded like they talking about D&D, needing a thief and that a hobbit would have a sneak bonus! It would explain how and why they get out situations sometimes like, "Legolas jumps in and saves the day and then leaves" or "the boulder somehow completely missed him and killed the orc." And it would explain why Gandalf couldn't be there all the time, the D.M. had to go somewhere and they decided to keep playing anyway.
Go ahead and poke some holes in my theory, I'd like to how to prove or disprove this theory of mine. I know it's probably full of flaws but it's fun to think that the reason that the Hobbit movie wasn't accurate was because the whole thing was actually just an RPG.