Final answer:
The least important reason a train operator should stay on schedule is because regular commuters can sense delays or track changes without needing to look at the schedule board, thanks to the dynamics of a busy commuter station.
Step-by-step explanation:
The least important reason for a train operator to keep exactly on schedule during rush hour is the presumption that a train which is longer than usual is certain that someone will grab the handle behind them. Experienced commuters, or 'regulars,' may not need to check the schedule board as they can rely on the movement of the crowd to inform them if a train is running late or if a track has changed.
This is due to the unique dynamic of a busy commuter train station, where people are adept at sensing minor changes in their environment, a skill developed out of necessity due to the fast-paced nature of commuting during peak times.