[1] as well as "the presence of people who deliberately flout the expectations" and whose non-payment must be made up, in expectation, by more honest customers.
I wonder how this came about? Like was this something a clever businessperson invented at some point? It sounds like the US is the only place with a tipping culture like ours.
In fact, I think, ignoring the tax evasion effect, the tipping system reduces profitability, because it scares away business by that "compensate-for-unpredictability" tax, which takes from what could be restaurant revenue.