From a nice long article on the history and psychology of tipping—which is of course as much about the tipper’s needs as it is the tipee’s.
In 1904, the Anti-Tipping Society of America sprang up in Georgia, and its 100,000 members signed pledges not to tip anyone for a year. Leagues of traveling salesmen opposed the tip, as did most labor unions. In 1909, Washington became the first of six states to pass an anti-tipping law. But tipping persisted. The new laws rarely were enforced, and when they were, they did not hold up in court. By 1926, every anti-tipping law had been repealed.