I think a lot of this has to do with a general lack of knowledge. Unless you are already a major name in any business, people rely on those who pay attention to offer advice from casting to personnel. As people become busier and more focused on their narrow specialty, they rely even more on "experts" on other people. Since most such "experts" seem to be merely the networkers we all knew in high school--not popular enough to be recognized and not pretty enough to be prom king/queen--that they rely primarily on the same system of brown nosing and favors that got them by in the past should be no surprise. The goal of everyone's life ought to be to find a way to do without these human scum.