I'm surely not the only American reading this and being flabbergasted at the wildly low consumer prices mentioned. I had to double-check the post date to see if this was from 1990 or something.
Yes, I tip at coffee shops. If you tip a bartender, why wouldn't you tip a barista?
Bartenders are often the only adult in the room acting like one. When was the last time you saw fighting, crying, fainting, hit and runs, etc. on the regular at a Starbucks? Bars can be like this in even the nicest neighborhoods.
Too much or too little security will discourage customers from staying or coming back. The bartender is running the whole circus. It's nothing like serving coffee.