Since we're talking about coffee shops: the Starbucks app allows to add a tip for a certain period of time after a a mobile order (something like an hour)

Do you use Square every day? The last time I went somewhere with specifically a Square reader was probably two weeks ago. Even if I went back tomorrow, am I going to remember my last experience enough to judge a tip?

Even if I go to the same coffee shop and use the same Square every morning, unless I'm holding a grudge it's de facto back to front end tipping rather than upon services rendered.