I hate the 15% tip! If they want us to blend-in, we should be tipping what a regular customer would be doing in the same circumstances. A couple bucks on a bar tab would be common and expected. It irks me when I have to leave 15% in a high-end restaurant. The waiter at the last shop I did was amazing. In the "real world," I would have left him 20% as a minimum, because he worked hard to make our evening special with exceptional service. Instead, I felt like I rated him as mediocre with a 15%'er.
Yes, there is a pizza shop near me where they want to you stiff the delivery driver. Nothing like pissing off the guy that now knows where I live. I'm not touching that reimbursement only shop.