Tipping At Fast Food Style Restaurants? Yes or No?

This is about fast food joints and not sit down full service restaurants. Please tip your waitstaff. They really rely on your tips to help supplement their income.

That being said, I have noticed something. Kind of a trend. I went to a fast food/sub sandwich/chain restaurant the other day. They made the sandwich right there in front of me. And when I went to pay with my credit/debit card on the display (kind of like the photo featured below) there was a tip option.

Credit: Square

Now, had I paid with cash, there was no tip jar there. And to me, no expectation of a tip for services. I have noticed this at a couple of fast food style restaurants. If I'm paying cash and even if I sit down inside of the restaurant (fast food), there is no expectation of a tip. And the only services rendered are them prepping and serving the food to you. Kind of like McDonalds/Burger King. But for some strange reason, if you use your card, more and more places are including a tip option on the electronic signing kiosk/tablet or on your paper receipt. And I for one think, that if I'm paying cash and not asked to or it's not implied that I tip, then why should I do it for paying with my card? BUT THEN...the guilt sets in. And in all honesty, most times I do leave a dollar (maybe two). Mind you, if I order from a restaurant for carry out, I'll even tip a buck or two per entree. What's the protocol for this? Do you feel pressure to tip at a fast food restaurant just because it shows up on the electronic display or on the receipt? Do you have no problem at all not leaving a tip at one of these places? Is it a guilt trip?

Etiquette says:

Full Service Restaurant - Leave a customary tip of 15% - 20%.
Buffet Style - (They provide a beverage & fresh plate service) - Lesser amount 5% - 10%
Fast Food Restaurant - No tip is necessary.

There is a science to this...from the folks that make the POS (Point Of Sale) Devices. They even talk about proximity to you when you're settling your bill.

Improving Customer Gratuity at the Point of Sale
It might seem obvious, but you should never do anything that makes a customer feel uncomfortable, that includes entering gratuity for them. Customers should never feel coerced into leaving a tip.

Here's an article from a couple of years back.