Wouldn't you rather be able to dictate how much those guys make based on how well they did their jobs?
That's nice in theory but how often do you actually do it?
Like, when I go to a restaurant, all I really want from a waiter is to be available in a reasonable amount of time and to not mess up the orders. And like 98% of them do just that. So I give them a standard 10-15%. It's not like I'm rating every waitress on a scale of 1-10 on a variety of different grading criteria. This isn't a video game review here.
Also, it doesn't really give you control over the type of service, since you do it afterwards. If you were required to tip as soon as you sat down, THAT would probably dictate the level of service you would receive.
That would be like Japan, where if they screw up your order, you just get a screwed up order and the manager chuckles about it.
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to measure the meaning can make you delay
it's time you stopped thinking and wasting the day