They have named you for a reason, so that everybody can call you by that one name to uniquely identify you from the other person. If you are sitting next to a person, I call you by your unique name to distinguish you from the other. That is how naming works.
With introduction of nick names, the classic functionality of names is endangered. If I call Robert, Bob, its one more name that I have to remember. And there are likely to be more people similar to the name Bob than Robert. I don’t want to address Nathanial by Nate. If your parents have named you Nathanial, they wanted everybody to identify you with that, not as Nate. I get confused. Moreover, I have to think twice on how to store your name in my address book. And if you are on social network like Facebook, Twitter, LinkedIn, you have different names for the same person. It even makes smartphones like Android* and iOS dumb. And I get even more confused when different people refer to you by different names. It even makes it difficult to search you on Google, Picasa or YouTube.
Why do we need all that mess? Why cant we have one and only one name associated with a person. Nick names/Pet names are inefficient, useless and they in fact invalidate the real purpose of names. If you don’t like your name, man the f* up. Live with it.