If we address a work with the assumption that the author does create an integral piece of artwork we can come to a greater understanding of the meaning behind the work. If, on the other hand, we conclude that a part of a work serves no purpose, or the author erred, or the part is merely historical then the resulting intellectual fruit is minimal. Understanding of the work is increased by assuming there is a point to all the parts; impeded if we assume only some parts have purpose.
The purpose, for instance, of Book 2 in the Iliad and the numerous scenes of slaughter seems at first elusive. But if the work is about anger and the violence that results from anger unchecked the violence is meaningless if the people upon whom it is perpetrated are faceless, nameless, uniform in their humanity. Book 2 consists primarily of naming the warriors, telling about their lives, giving human detail to the combatants. Thus when the violence occurs we are seeing not just pixels exploding but the death of human individuals with hopes, worries, thoughts, lives all their own. This heightens the drama of rage that the epic seeks to convey. The peace of book 2 is paralleled by the funereal games in book 23 which again shows that these are not just nameless extras on a set but humans who engage in human activity, love, suffer and die.
I have yet to figure out, though, what the purpose of some other sections of great works have to do. What, after all, is the purpose of Leviticus, Numbers and Deuteronomy in the overall story of the Jewish people? Couldn't the inspired word of God convey the message of salvation of the people without these tremendous long lists of laws and names? What point do they serve in the context of the unity of the Old Testament? Or in relation to the New Testament? Or in the work overall?
Similarly I have yet to figure out the purpose of Tom Bombadil in the Lord of the Rings. Assuming that there is a point to the figure what would the point be? Was Jackson right when he cut out that whole section of Bombadil and the barrow downs? Did the work suffer? Would LOTR be the same w/o the Bombadil/Goldberry section?
I tend to think that there is a purpose to the section. Certainly it would make sense with an author as meticulous as Tolkien was reported to be that he would not have included three, I think, chapters that were utterly meaningless in his work. So what point is the Bombadil section?