If you are being paid $15 dollars per hour to wait on tables, I am not tipping. Been to Europe, tips are appreciated but not required. Unlike others I did get good service in Europe. At one restaurant, I left a five euro tip. My son’s fiancé picked it up and handed it back to me, she is from Europe. She said it is not required nor was the service so good it warranted a tip. Only in tourist areas, with lots of Americans, do they look for tips.
They don’t expect tips, and a large tip would probably insult many. But a small tip for especially good service is appreciated.
You probably had good experiences because you made the effort to understand the culture and behaved in accordance with it. Lots of Americans don’t, and then complain that they get poor service.