Fast, frequent and dependable trains make cities, big and small, more attractive places to live and do business. They have, essentially, a positive domino effect:
It begins with a lower cost and more attractive way to travel.
Then, visitors arrive on the train, walking from the station, patronizing local stores.
The local stores, combined with the improved transport options, lead people to move closer to the train station - leading to more people traveling by train.
Which means even more visitors arrive on foot, needing better public transit to reach their final destination.