I'm sure they are all deserving courses; the few that I've been to are most excellent. But it's kind of a perpetuating cycle. People will go to the courses in the top ten, so they get more reviews, and chances are more 5* reviews out of a preconceived notion or fear of thumbs-down.
Like, oh, this is a top 10 course, it's a 5 no doubt. Maybe not for the trusted reviewers, but for the person who does one review.
Conversely, the courses that don't qualify due to the lower # of reviews are a lot more hidden, and won't get the exposure, or have the added pressure of thumbs down for a less than stellar rating. It almost skews the ratings so the top ten get higher ratings, IMO.
But, based on the abuse idlewild has been getting, maybe not...