I wonder if anybody knows why Gatsby is not called by his first name?

In the book The Great Gatsby, everyone is called by their first name, Myrtle, Catherine, Daisy, Tom, Nick. But Mr. Wilson and Gatsby both are called by their last name. Is this a sign of the lack of respect both characters have in the story? Nobody ever gets really close enough to either of them to really appreciate them. Could someone give me a link or explain this to me?