I'm genuinely curious as to your intentions in asking this question. Did your parents tell you that you are perfect? Have you told your child or children that they are perfect? Have you heard another parent say it to their children?
Have you ever met a child who acts like a little snot? Thinks they are better than everyone else? A little like Malfoy in the Harry Potter series? Should any parent want their kid to act like a Malfoy? (Remember what he was REALLY about - thought he was God's gift, bullied people, but was really a coward...) Making a child think they are perfect turns them into this kind of kid. And then as they grow up, they find out that their parents lied to them.
Children need to hear good things about themselves AND constructive criticism. Without both, they can be emotionally stunted.
Finally, why does a parent do this? To live vicariously through their child? If their child is perfect, that must mean that the parent is perfect? So is it really for the child or for the parent? If it's really for the parent, it's selfishness.