Some people endeavor to portray a persona.
Some people perpetuate the beliefs of their parents.
Some people pretend to be somebody they've seen on TV.
Some people have trouble accepting that they're actually existing. 
Some people perceive themselves as being unlike anyone else.
Some people have an aversion to personality profiling.
Some people just can't help themselves. 
Some people feel a need to place everyone they've ever known into categories.