If this is true, and we have to let Alduin eat the world to prevent something... worse (sounds funny I know) from happening, then why would they allow us to keep playing after the main quest is done.... Maybe we can play as seven year olds?
Ah, but even if Alduin eating the world is something desirable when taking the long view of causality, who is to say our character, and their supporters will be wise enough to realize it?
Think about it, what if by some terrible twist, Alduin's eating of the world is required because Nirn has an expiration date? And that by possibly stopping him forever, we have prolonged our existence superficially, but the world itself is destined to die in the end anyways after a certain amount of time.
In the eyes of short-sighted mortals, we have saved the world, but in the eyes of a superior being, we have doomed our existence to a final death with no possibility of rebirth or renewal.