I mean every book has major themes you can use to rationalize the smaller events. In Of Mice and Men, why did they come to Curley's farm? Because Lenny is on the run. What theme does this inherit? That dreams are repeatedly deferred by our sometimes literal heavy-handedness. And it's a fragile, costly balance between toeing the line like George and harboring these dreams at all, like Lenny does. You can read a book at face value but if you want to teach a book you need to keep track of themes and larger conversations.