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.