Why shouldn't they be? The idea that if you don't rate yourself highly no one should is just an excuse for shitty instincts.

Obviously it's a useful piece of nonsense to tell yourself. People are more likely to come to your side if you are confident. But the explicit reasoning is reprehensible. (not that any explicit reasoning probably went in, it's such a common idea that it is repeated without thought. It's almost a universal applause light.)

This is more of an irrationality quote. A bit of of paper thin justification for a shitty but common sentiment which it's useful to adopt rather than notice.