Why do they call you 'boss'?

Every time I go through the drive through, or even at many check-outs they say 'Ok boss' or 'yes sir boss' or how can I help you - 'boss'? At the Dairy Queen it happens without fail. I'm not their 'boss' and the next time they say that I'm tempted to just say something like...

[media=https://youtu.be/CHzdxly0Y9Q]