I think to often, on or both sides of the equation of a relationship, thinks they can fix or change the other side. When neither side wants to change or doesn't believe they are broken. It is sobering for a person to find out that their partner believes them to be broken or fixable. It is one think to see potential in someone to the point where they might grow into something. But to often, people engage into some kind of social/interpersonal engineering with their partner to create what they believe they should have from a partner.

Again, I might be full of shit. There is a good possibility.