People who work in 'fast food' or coffee houses very often do so because it is the best they can do at the moment ...
Both my kids worked as wait staff during college ... it is very difficult work at less than minimum wage ... and quite often they get stiffed ... these people RELY on tips ...
There is an old saying " Walk a mile in MY shoes ...
Give me good service and you will get a generous tip ... JMHO

PS ... At the restaurant I 'sub' in, the management puts a tip jar out, even though it is a good paying gig ...