I was just in Hong Kong...and people don't tip taxi drivers or most other services.
In Thailand, even a $30 meal, you only leave about a $0.50 tip.
I always get a lot of small bills as soon as I land so I can tip...and I ask the taxi driver to teach me the tipping rules on the way from the airport to the hotel (of course, then you have to give them a good tip for the information. hehe)