[Mithadan]

from the perspective of storytelling, the climax of the story is the Battle of Five Armies and Thorin's death scene. To add chapters after this about how Gandalf and Bilbo came across wolves, stray goblins or mosquitos, or that they ran out of food would be rather anti-climactic (excuse the pun). Of course, one could argue that Tolkien did exactly this in LoTR.