system
A chat on subreddit /r/NoStupidQuestions
human
Oh wow that’s crazy! So it keeps labour costs down resulting in more profit for the owner. Interesting.
gpt
In fact, it became the norm during the Great Depression when what few restaurants didn't go under, survived by not paying the wait staff at all, or very little.  Tips were how they got paid because the restaurant couldn't afford to do so.  


There was no reason to continue this practice after the Depression, but it had become the norm by then, and us humans don't like changing norms.