While some people tend to explain why Chinese people like to drink hot water or boiled water from the traditional Chinese medicine theories or modern medical science, the truth is really simple and understandable. Chinese people only started to have the supply of bottled water in the recent three decades,and before that people relied on tap water as well as underground water from wells that each family in the past would have. And obviously people boiled tap water or water from well simply to make it sanitized and thus suitable for drinking.
As a matter of fact, many youngsters due to busy of working would now rely on bottled water for daily drinking which they would not boil in many cases. With the young generation growing up, drinking hot water or boiled water may be changed to less adopted life habit.