It's the request for a tip at practically every cafe or donut shop, where a person is simply pouring drip coffee or placing an item in a bag, for to-go/carry out, which gets to me. Or the expectation to tip for a re-fill of a coffee mug, at a cafe. It's not service-- it's dispensing a product.
I am starting to wonder how much baristas make, for example, if it's $10-$15 per hour, plus 15 customers per hour (x$1-$2 tip each)... that's potentially $50-60k+ per year. Which is more than many teachers and healthcare workers make-- people with degrees, training, and who provide a skilled, emotionally-involved service.