Doctors, lawyers and CPAs are instructive examples, as they have far stricter credentialing than software engineers. Doctors probably being the most strict, lawyers next, then CPAs. Particularly with doctors, the total amount is tightly controlled by the number of seats in medical schools.

My fiancee is a high school guidance counselor, and she essentially did a demo session with some current students during her interview.

I don't like the situation we are in, but I think your examples actually help illustrate why things are the way they are: we don't have a gating mechanism into our field. Most of your other examples do.