Why are some people so afraid to talk to their supervisor about a concern that is generated by a comment or action that the supervisor said or did?

It’s understandable if the supervisor has a track record of terminating any employee for minor issues, so let’s leave that out of the equation.

I’ve reported to more supervisors than the number of jobs held at the same company for 25 years. Not once did I ever fear going to a supervisor and letting him/her know if something that they said or did didn’t sit right with me. It always resulted with a positive outcome. They explained their point-of-view, and occasionally there was an apology for coming across in the way that I took the initial meaning.

The results of these conversations were a peace of mind, not dragging down the dept. morale by venting to co-workers, and building a level of respect between my supervisor and me. It was also helpful to give them positive feedback when I felt that they were on the right track. After all, they are human, too.

What keeps people from approaching their supervisor with any concerns?