It actually started in Europe, and came to the U.S. after the civil war, and there were laws passed against tipping in some places but they all were repealed and it's a fact of life.
https://www.businessinsider.com/history-of-tipping-2015-10
Personally I have no problem with it, I like giving people tips.
But critics have said that allowing the minimum wage to be so low for tipped staff basically creates a two-tier worker system, and that it encourages discrimination by staff who are trying to serve what they think are those who are more likely to leave a fat tip.