So where does the percentages come from? Why do you arbitrarily decide on that number?
Surely the cost of the meal doesn't correlate to the amount of effort they've put in?
Surely rewarding bad behaviour and bad service is contradictory?
This is how I feel. I don't tip bad wait staff because that only encourages their bad behavior and effort. How do they know that they would've gotten 20% from me if they performed better? Others have said they tip 10% for good waiting so maybe the bad waiter/waitress will think they did good?
I agree with your middle point too. Just because I ordered a more expensive meal or less expensive meal, you should get a better/worse tip for the same service? The whole system doesn't make sense.