Even some CFIs. I had an older CFI say he was going to follow me in, then say he lost sight of me. Next thing I see he's turning final in front of me at a higher altitude. I let him know he cut me off in a "meh, no biggie, stuff happens" tone and he goes off about how I screw everyone up by flying such a wide pattern, never mind I'm going a good 30 knots faster than he is.
Then I'm putting the plane away and he comes over and explains he was mad because his student was about to solo and I made her go around and she'd never had to do that before. Uhhhh..... Doesn't give me a lot of faith in the training people are getting.