Nonsense. In my experience (granted not 20 countries but more than a dozen) the service is at least as variable and often worse in countries where tipping is common. Also, it encourages behaviour that exists only to extract a larger tip.
Just price the goods correctly so that I know when I start the transaction what I am going to pay, then I'm more likely to return to your establishment to enjoy the food and service.
That has also been my observation. However, where the US stands out alone for me in the developed world, is that tipping hasn't just become common in a few isolated situations - like getting something served at the table or getting ones' room cleaned. I can somewhat understand those because you as a customer can judge best how labour intensive / stressful your particular case has been for a low paid worker. But in the US it's everywhere. Why the hell do I have to tip a hairdresser? A taxi driver? A gas station serviceman? They have prices based on workload and materials anyway, so please, why do I have to figure out your correct salary for this interaction based on some arcane percentage system myself? This, at the end, is just what I call unprofessional. If you want to see how professional the service industry can get - as others have pointed out - just visit Japan.
Just price the goods correctly so that I know when I start the transaction what I am going to pay, then I'm more likely to return to your establishment to enjoy the food and service.