Tipped workers in the United States come from all ages and backgrounds.
When it comes down to it, those tips mean the difference between paying the bills and not. And to my friend's point: In Germany, most service workers are actually paid well. Tips are basically a little bonus. Not here.
And these folks work for $2.13 an hour before tips even come into play; when they get stiffed, that $2.13 is, frankly, totally absurd.
So ... in another country where people are compensated fairly, feel free to make tips optional. Otherwise, consider what happens to these people who work every day for a living.