I would argue that there should be way more Michelin-star restaurants than exist, but they artificially cap the supply to keep them rare. It's a form of the same thing.
I think there's an incentive system at work that I'm not sure I've seen articulated before. If the people controlling a rating system want the best ratings to be rare, they will often have to resort to a combination of opacity, arbitrariness, and fine distinctions that are largely meaningless to the consumers of the ratings. Because True Quality can't be reliably recognized by some ratings committee... and yet, they must rate.