I rarely feel that I shouldn't tip.
Only at a very expensive restuarant that explicitly states that gratuity is included or poor service.
And that's only because I don't have the funds to double-tip.
At average priced restuarants and especially my pizza dude, I pay 20%--even if it's claimed to be in the price. I asked my pizza dude, "why is it this much when the price was that much" "delivery charge" he replied. "what do you get from that? .50 cents?" "Yeah"
"Well here's $5"
The price is what it is. I tip for service and I want my servers to remember me fondly. I don't imagine that I'm making anyone wealthy, but my pizza deliveries are always piping hot and a fiver buys a sixer so I doubt it goes unappreciated
Now my wife, she tips like a loon. But that's because she *only* makes tips and she wants to makes sure women know she appreciates them.