I don't think anyone ever put forth that notion that there was supposed to be.
They could have done this all in secret, no "contest," no "list," just an announcement "We will now be adjusting lumnis on a dynamic scale based on how a sampling of players hunt."
But they did us a solid, they dangled this meager carrot of another fame list (list with no importance), and called it a contest, to inspire people to boost the average. But in general they are not looking to help the populace as a whole to advance faster (as if this isn't already fast enough), they just want to help the casual players keep up. The average can go up, the average can go down, it is the ratio that matters. And giving a reward to people who are already at the top would actually make the ratio worse.