So, I guess its time for an episode of “Dragonwriter Ruins Adam Ruins Everything”.
Americans imported the practice of tipping from Europe just after the civil war (some accounts say as an excuse for restaurant owners not to pay newly-freed blacks working as servers, but that's less than clear, though where such workers were common, it was certainly leveraged for that purpose), and there was criticism of the new but rapidly-spreading practice as unamerican and pro-aristocratic in the late 19th Century, before prohibition.
Heck, here's a pre-Prohibition (1916) book about the practice of tipping in America, which even recounts past legislative efforts to stop it:
http://www.gutenberg.org/files/33170/33170-h/33170-h.htm
So, no, it didn't start in response to Prohibition.
all while making the client be the jerk.