[Blarg]

Yeah I get this all the time. It seems often the cashiers stop listening as soon as they can and start going through their mental checklist of things they're supposed to do -- do you want to supersize it, do you want extra cheese, for here or to go, would you like to try our new X, whatever.

They just completely shut down so they can start up their scripts. And they're not bright enough to handle varying from the scripts at all. They aren't listening for anything but the answer to their question and probably don't really give a damn what you're saying. They're on auto-pilot the whole shift.

I have had some of the stupidest encounters with staff imaginable at fast food joints, over the simplest thing, and they aren't infrequent. I'm like the poster boy for politeness, but still it sometimes really grates on my nerves. Talking to someone who's not listening is one of the stupidest experiences on earth.