How come we like to pretend we're unique and not ordinary?

a lot of people when you tell them that most people do this or act this way, someone will always use themselves as the exception. "Im different" "I don't do that" "Everyone is different". You hear this stuff and people just want to make it out to look like they're unique and not part of the masses
How come we like to pretend we're unique and not ordinary?
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