Every time tipping comes up on HN, someone chimes in to say what a strange American custom it is, and how nobody ever tips in Europe.
Historically, tipping came to America from Europe in the 1920's and 30's. When it started, it was very divisive and considered un-American. You can see it in the background of certain old films of the era. It is a sub-plot in the Humphrey Bogart movie Petrified Forest.