There is a time and a place.
First of all we do it because, as Calvin pointed out, we have to work with one another. Everyone has feelings. When feelings get hurt people naturally take it out on the one that hurt them. That usually results in distrust, revenge, less collaboration, and less productivity.
Second of all, who are we to condemn others? Everyone has faults, including us. The challenge is to be big enough to look beyond the traits in others that "drive you crazy" and help bring out the traits that foster productivity, both in ourselves and in others.
Faults can be addressed, but there is a time and a place for that. In order for someone to really change they have to be open to the idea. They have to be humble enough to ask themselves, "What's wrong with me?" People are seldom in that situation. So, when someone complains to them they just put up their guard.
Lastly, the right person needs to address the weakness. It is certainly not an impatient coworker. It needs to be a trusted friend or loved one. However, even when a trusted friend or loved one points out a flaw they still need to be humble. Otherwise they will immediately call "foul".
