Are there any examples of other skills where the distribution is bi-modal?
Good question. Maybe something where you have to get into a guild to be really good, and if you don't get in, you're going to be one of the lesser group.
Something like accountants.....there are the guys who make it to CPA; anyone can do it, but it's a lot of effort, and getting half-way there doesn't count for much. So there is one group of CPAs who are really good, and all the non-CPAs are just expendable or something.