I rarely frequent this type of establishment, but have been to a few where they expect a tip for basically counter or self service.
I tend to pay cash anywhere like this, but if I were swiping a card, I'd hit no regardless and at the end of my visit, if I felt a tip was warranted, I'd give one in cash, directly to the person who earned it.
Even when we eat out and do use a credit card (which almost never happens anymore), I leave a tip in cash.
Different places have different rules for how tips are collected and split, but in my opinion, food service workers work hard, for little money and I want them to be able to have cash on hand, decide what they want to report or not, split with other employees or not.
My son's girlfriend is working her way through college waiting tables, and some establishment's rules regarding tips/splitting/reporting are simply ridiculous, so the last thing I want to do is document that tip. I'm paying that person directly who served me, and what they choose to do with it and how much they reveal they made is up to them.
And if service is really bad, I have on rare occasion left no tip, and complained to management. For good service I will tip between 20 and 50%, more if the mood strikes me.