I find myself almost irresistably drawn towards the conclusion that people will game the hiring process, because it is a game. It has winners and losers. Everybody is trying to make themselves look better than everybody else, even to the point of making themselves look better than they really are: Job candidates, employers, internal and external recruiters, everybody who is selling a hiring product, etc. Everybody is trying to emphasize their positives and hide their negatives, while searching for the negatives of the others.
A drawback to "do your own thing" is that it is enormously inefficient for candidates, and the results may turn out to be based on the luck of a particular candidate guessing a particular employer's game is, or being generally better at games.
I don't know a solution. What strikes me is that as broken as the system seems, we still manage to hire good people most of the time.