At the original poster: I used to ponder the same exact question. The way I now view scores is as a living spread between corps that evolves throughout the season. I am of the opinion that a larger score spread would allow for a more organic growth through the season. When I first started dealing with scores in the marching activities I tried compartmentalizing everything. I tried assigning abstract point values to specific elements of design and levels of execution. The problem with this way of thinking is that it implies that the content scores never change (which is far from true).
Similarly, comparing the finals week score of 13th place corps X to the early/mid season score of the Blue Devils is comparing apples to oranges. The content is totally different, and one show will always have more effect, regardless of the score or when it was given. Like I already said, a larger score spread would feel more natural in this regard.
In the end, who cares, right? The score is just an extrinsic motivator for corps to base their progress. In 10 years when I pop out my 2014 DVD, I'm going to watch the shows that I enjoyed, regardless of the score it was given.