"It is difficult to get a man to understand something if his salary depends upon him not understanding it."This is another one of those quotes that is both true on the surface, and also true at a deeper level. At the surface level, people believe that their jobs should be protected.
For instance, union steel workers will agitate against free trade in steel, because they don't want their jobs to disappear due to lower cost imported steel, even if it would benefit everyone else. And teachers don't want to admit that it should not be as difficult as it is to fire a bad teacher. As an example - a teacher friend of mine told me about a math teacher colleague who was a truly horrible teacher. A two year process was ongoing, which would likely culminate in the firing of the teacher, but still - two years! My teacher friend, through connections, managed to engineer it so that his children didn't get this teacher. Other children weren't so lucky.
It reminds me of a project I once worked on. Because of some peculiarities in the company, it was wildly, insanely overstaffed. It was also a very poorly conceived project, which is another story.
But I was talking to a project manager on the team (there were about 5, there should have been 1, max). We were talking about the over-staffing on the team - which we both agreed on. But it turns out that in her opinion, it was not HER team, and in particular not HER job that was unnecessary. It was everyone else's jobs.
At the deeper level, what this illustrates to me is that self interest is paramount in people's minds. And it's not just about money, it's also about reputation, power, all those things.
There's probably some evolutionary cause for this. I remember reading a book on evolution, which suggested that people are hard-wired to believe in a version of events or a philosophy that benefits them, even if it don't necessarily make sense. The theory was that this would make them more vehement and convincing when they're arguing for their "rights".