When we hire someone for a job, we want someone who is "good" at what they do. By this logic, we pick someone in the top 10% - a notion which will vary from person to person.

Now consider a job market, where employers are looking for candidates. Employers what "good" workers, candidates want "good" jobs. All the activity will be concentrated around the top 10% of each side.

The situation will be better or worse depending on correlations among everyone's definition of "good". This has nothing to do with chess, sorry!