Always love this one when it comes up.
15% added regardless of the quality of food and service.
Of course we are to assume that good is the "norm" and we know what to do with "great", right?
But what about sub par? True, we can ask to speak to the manager but who's kidding whom? Most of us are reluctant to make waves.
So our options?
1. Don't go back.
2. When asked, be honest and relate your experience to others when asked.
3. Find alternatives that are not quite as greedy. They are out there.

Thanks to you, Pat, you hit the nail on the head!