Thats if you think of tipping as leaving a tip or not leaving a tip. Its not so black and white. To me anyways, it seems like most people tip 15%, thats it, no matter how good or how bad the service. I think most service deserves a tip, I never, no matter how terrible the service leave nothing, 10% is the minimum I leave, thats for terrible service. I will leave 15% for average, and depending on quality of services from there I will leave up to 40% or 45%. If people rewarded quality service more substantially we would see more quality service, but they don't, its 15% all around, no matter how good your service is.
I guess where we differ is that you feel it is not of poor etiquette to leave a $0 tip. I feel that anyone making $4 an hour serving me food, even if they do it poorly, deserves a few dollars tip. Now had the person served me in a fantastic manner, they probably would have walked away with $15-$20 instead of $5. I think we both agree that if you do something poorly you should not expect much of a reward, we just disagree how small that reward should be. Its like being the poorest employee at a large company, even you get a small bonus.