Why do customers expect sit down service in fast food restaurants?

I was leaving for today and some old lady was like can i have more salt. I said yeah there's some on that stand over there. Im not getting any for you im off the clock and i don't wait tables.

There was another time i was on break eating my food and some old lady asked me where her milkshake was. I said ask the front counter. Im on break dont talk to me