KAUSpilot points out something very important that many may overlook:
wait people in America are legally allowed to get paid much less than the official minimum wage
...so their paychecks are used mostly to cover their taxes, which are calculated based on a percentage of (assumed) tips on sales. So, a paycheck may be anywhere from absolutely nothing up to about $30 or so.
The tip should never be related to quality of food or other things not in the control of the waiter. Certainly poor service should see a reduction or even elimination in the tip - but a proper explanation should also be made.
This is purely subjective of course, but service in non-tipping nations, especially Europe, is as you would expect it to be from waiters who earn the same amount for good or bad service, for fast or slow service - its lackluster and uninterested at best and non-existent at worse. Finally, the prices for everything in a restaurant or bar is more expensive precisely because of their non-tipping regime.
So you get in the rest of the world:
---unenthusiastic service / high prices / no reward or punishment for good or bad,
or in America you get
---usually good service / lower prices / the ability to reward or punish for good or bad service.
This is just another example of America's stance as a hyper-capitalist country where individual effort is rewarded, and failure punished. Often, the less-capitalist way can end in the same result - but in this case, I can see no advantage whatsoever to compensating someone to wait tables or tend a bar the same amount regardless of speed, friendliness, or efficiency. Like all service jobs, these people should be incented to perform better, not rewarded for simply showing up for work.