I'm not saying that you're wrong, but isn't there also an obvious incentive for someone in a managerial position to insist that the people that they manage are doing important work, because it raises the profile/importance of their own position in turn?

I suppose this thought is probably an overly pessimistic viewpoint, but generally speaking, many people want to justify the importance of their work so they can continue to be employed - it seems logical that if you're job is to manage others, then a very big part of what your job actually is, is hyping up the importance of those peoples work to justify them needing a manager.