What motivates referees? Beyond the paycheck, what do they do on their job that makes them feel proud (where they say to themselves, "I was great today.") Is their anything besides "I didn't make a mistake"? They get graded every week and so, of course, they probably like getting favorable evaluations. Seems likely that there is an ego thing about having millions of people watching them doing their job and feeling proud about performing on the biggest stage.
Obviously it would be bad for a ref to try to fix a game. Someone on a power trip also would make a very bad ref. I wonder if there is a "professional culture" for refs and if it needs some adjustment.