Tipping Isn't Necessary
This custom is actually pretty common in the Eastern hemisphere. In China, some workers may deem tipping to be offensive as it may seem like they're looking for a handout.
In reality, service workers in Chinese are paid average wages so they don't need to be tipped, while the Western hemisphere pays service workers under minimum wage (on average of $2 an hour) so tipping is necessary. Also, fun fact, it's against the law to tip in a Chinese airport!