I agree with that. Since I'm in the US, I pretty much have to tip in order to be a decent human, and I habitually tip 20% or a touch less. I understand that NZ has different expectations, so you're fine leaving no tip. That's what makes the world go round.
I would hazard a guess, however, that some of the people on the list (Sean Penn would be my first guess) are in the US and yet take an attitude that "Tipping is evil. Many people in other countries don't tip. They are so cool. I will be cool too! The restaurant owner is depriving his wait staff, and if I withhold my tip, they will rise up and demand that the Rich Boss give them better pay! By not tipping, I am really helping my waitress have a better life."
I've known plenty of self-serving Liberals here in the US who think like that.
When we go to a “tip the staff” type establishment, the “tip-o-meter” starting running the minute we walk in the door. We tip based on service and product, not a preconceived percentage. Sometimes we trip great, but there have been times we left nothing..except feedback for the manager.