I’m in lower Queen Anne. Every corner store that also sells coffee/sandwiches does this. Maybe 1-5% of customers are buying a sandwich, but 100% are prompted to tip with an 18% default.
The problem is that it seems to be necessary to prompt every transaction for a tip to collect any credit tips at all, or at least all the major POS are set-up that way.
Which doesn't seem like it should be a big problem in an already not tip-heavy, but there are a surprising number of people who make a very big show of not being able to tip because there's no credit option.