I leave a tip only if I am satisfied with the service in the restaurant. I'm not too picky, I did not leave a tip just two times. Once I waited for the waiter for more than 20 minutes, while apart from us only a few tables were occupied. The second case was when my wife and a waitress had a row in a cafe because our son (he was only 2 years old) had been eating carelessly (I think my wife or I would have cleaned after him table and seat, as we did before, if the waitress didn't start a quarrel as soon as he poured out the soup). Both times it was a roadside cafe. I sometimes leave a tip where I like to communicate with people. For example, a courier who often delivers me goods from one online store. I'm glad to chat with him for a couple of minutes and usually leave a tip. I leave a tip or pay extra for services that I additionally provided.