Why doesn't every character have a surname in Avatar? I know it is quite an unnecessary question but it struck me that Asami, Hiroshi and Zhu Li has a last name but no other character, or maybe some ... well, you get the point.
I have read the "Names in the World of Avatar" page and one possible explanation I can see, is that given names describes the characters (if translated to some of the Asian languages), hence surnames being needless as they are already described enough.
Maybe they had to give Asami and Hiroshi a last name to explain why the Satomobile is named Sato but still...