It's even more interesting when we remember that in western culture is rude to speak about a present participating person using third person pronouns (- "hey, I'm standing right here!").
Using "sir" everywhere you'd say "you" feels like the same sort of high respect that merkitt was describing in Sinhalese. I think the reason it comes across as rude is that the only context in which you'd be likely to hear someone do that in person is to mock. In the same way, some men become offended if you refer to them as "sir" at all, even upon first greeting, possibly out of a suspicion that they are being mocked.
You also get that kind of thing at snobby restaurants / hotels / other services that cater to the rich, "would sir like to see the wine list", etcetcetc.