Because there's a noticeable trend among people wearing the mentor crown that they act in very non-mentor ways. They won't help new or struggling players or even complain about their performance. They are suppose to be examples of good player etiquette (as that box we all tick indicates) but there are many who are far from it. Now, a lot of this is SE's fault. They give too many rewards for being a mentor, so people who just want the mount abuse Mentor Roulette. They need a specific mentor feedback system for mentors so bad mentors who don't uphold good player etiquette can be reported and have their status removed.