Everyone takes criticism so personally. Even on the professional front. If you tell someone that there's still some scope for improvement (and that's sometimes putting it very mildly), all hell breaks loose...people react in their specific ways...sulking, angry retaliations, defensive answers, etc. Goddammit, it's just your work I'm talking about yaar. Not making some value judgements.
People sometimes forget that there's always a specific clue in criticism as well.