People are thinking in terms of grades
That's not an explanation, just a symptom of the problem. People of mediocre talent and high talent both get A - that's part of the reason why we have to use standardized tests with a higher ceiling.
My intuition is that the top few notches are satisficing, whereas all lower ratings are varying degrees of non-satisficing. The degree to which everything tends to cluster at the top represents the degree to which everything is satisfactory for practical purposes. In situations where the majority of the rated things are not satisfactory (like the Putnam - nothing less than a correct proof is truly satisfactory), the ratings will cluster near the bottom.
For example, compare motels to hotels. Motels always have fewer stars, because motels in general are worse. Whereas, say, video games will tend to cluster at the top because video games in general are satisfactorily fun.
Or, think Humanities vs. Engineering grades. Humanities students in general satisfy the requirements to be historians and writers or liberal-arts-educated-white-collar workers more than Engineering students satisfy the requirements to be engineers.
That's not an explanation, just a symptom of the problem.
This is what I was trying to convey when I said it might be another example of the problem.
I think it's reasonable, in many contexts, to say that achieving 75% of the highest possible score on an exam should earn you what most people think of as a C grade (that is, good enough to proceed with the next part of your education, but not good enough to be competitive).
I would say that games are different. There is not, as far as I know, a quantitative rubric for scoring a game. A 6/10 rating on a game ...
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