Dont you wish we could just 'know' each other and not have to label and package everything?  Knowing ones last name means nothing if we dont know things about ones charachter, thoughts, feelings. I understand putting a name on a form etc, but really it's such a base identifier. 
Curious, would you find it more comfortable to be asked why your names are different, or how that came to be? Would one question be more or less intrusive than the other. Would it matter if it was a stranger, or new friend?