Thank you Sir? What the fuck?

So I have come across something strange. Whenever I buy my java at any place not Uncle Buck's, people say thank you sir.

It baffles me.

I mean first of all I am not knighted. Yes does my Irish name that is my grandmother's maiden name come from Irish nobility, back a couple centuries, of course. But, don't call me sir.

Additionally, you're handing me the coffee, I say thank you or thank you very much or thank you, thank you very much or thank you much. I prefer the thank you, thank you very much.

Weird.

Another thing I noticed, I think people think I am a cowboy or something since I say howdy.