It's one of the cornerstones of going to any kind of company that provides a service to you: it's imperative that you leave a tip. This is especially true when it comes to something like a restaurant or café, where it's basically expected that the customer makes up the wages of employees.
Plenty of places can get quite unhappy if their workers don't get their fair share of tips, so when a business decides to operate without them, it can get confusing to say the least. This seemed to be the case when @fuckyouiquit posted a sign which asked customers of an anonymous establishment to refrain from selecting the tip option on their payment screens, not only because the money did not go to staff, but also because their company policy did not permit tips in any form.
Understandably, some Twitter users were incensed by this seemingly cruel approach, although others wondered if it might have a more logical (and ethical) explanation. Either way, it's not the kind of thing that your average customer is used to seeing.