I got into a very interesting discussion with a group of pretty frequent international travellers the other day. It was around tipping the maid service in hotels.
Some - like me - never do it, and to be honest had never really thought about. Others were aghast at this and said they tip every day, leaving money on the pillow or nightstand. Going rate was about $5 iirc.
What fascinated me was that most people on both sides stared at the other side in astonishment. Our group was pretty evenly split, but had a lot of Americans which favoured the 'always tip' group.