A train pulls in alongside a crowded platform. It is precisely on schedule. The train is not full, and yet nobody boards it. All trains that stop at the platform travel to the same destinations. Why then did nobody board the train?

“The passengers missed the train.”

While it's possible for passengers to miss a train, the riddle specifies that nobody boarded the train at all, indicating a more fundamental reason for the lack of passengers.

“The train is out of service.”

If the train were out of service, it would not be precisely on schedule, contradicting the information provided in the riddle.

“The platform is closed to passengers.”

If the platform were closed, the train wouldn't be able to pull in alongside it, which contradicts the scenario described in the riddle.