I know a few people who do it - not know well but it seems to be a type of person.
You ask for something to be polite but it's perfectly reasonable - 'could I have a carrier bag please?'
They look at you poker faced and say 'no.'
You wait.
They break out into a grin and say 'course!'
I know it's meant harmlessly but I hate it. I feel like such a twat as I stand there waiting for the 'punch.' AIBU to wonder why the fuck people do it as it isn't funny!