And I can't believe you posted what you just have, QFI. After all these polite replies, which boil down to common courtesy, you haven't seemed to understand that everyone has answered your question. Some people use "Sir" when they have the time/feel so inclined, and some don't. It's not in our books so it's up to the individual. There's no partcular history or reasons apart from those offered.
Looking at your lead post, which you've encouraged us to do, there's nothing in the English language that I know of that gives us the intent of what you think you want. Take a deep breath, re-read the replies you've got and understand that you've got what you asked for, SIR!