For each of these famous people there are unfortunately also less famous examples of individuals who were utterly incompetent and did things like design earthen dams for example, that failed and cost people their lives. Not to take anything away from the great ones, however it is the lowest common denominators that a state is obligated to protect people against, hence licensure laws.
For some of the great ones listed, they lived at a time when the activities they were engaged in did not require licensure. It seems that they would have had no problems knocking off a test of minimum competency. Sure they would have had to study, but they were geniuses. No big deal.
Even today there are firms with non-licensed 'engineers' as CEOs of the their firms. They may have a little trouble leading the licensed guys and gals, and many would never work in such a firm, but these people are doing very well, thank you. However, everything that goes out of their offices bears the stamp of a licensed engineeer.
There are still good engineers and less good engineers, and there is, was, and always will be the prima donnas. I imagine Huff got taken down a knotch or two by the NASA boys. They probably tried it with the k-guys and got blasted. Murch probably has his head screwed on right, just wish we could hear from him once in a while.