No time is wasted. The bullet train is moving all the time. If there are 30 stations between Beijing and Guangzhou , just stopping and accelerating again at each station will waste both energy and time.

A mere 5 min stop per station (elderly passengers cannot be hurried) will result in a total loss of 5 min x 30 stations or 2.5 hours of train journey time!

A 5-min stop is actually a longer delay owing to the time spent accelerating.