I feel like these protocol'd orderings are useful because they eliminate one source of politic-ing. There's nothing to read into the seating order or serving order when it's all by the book. There's no worrying about "what will the bishop think if you serve the baron first?". Your rivals and your guests aren't trying to read into your actions (at least in this sphere).
It's true that any arbitrary ordering would suffice (for example, Olympic parades are in alphabetical order), and that the orders chosen are basically the agreed upon overall social/political order, it still serve similar utility.
Except when there are two books. The old guard, and the progressive. “Will the host turn the traditions around and serves the guests by alphabetical order, or will they keep serving the oldest people first?”
It's true that any arbitrary ordering would suffice (for example, Olympic parades are in alphabetical order), and that the orders chosen are basically the agreed upon overall social/political order, it still serve similar utility.