It’s a city builder, then, as much as it is a straight management game or a 4X. It's the difference between starvation or survival. There’s a difference between a handful of squat cave-dwellers traversing the map’s width on foot to eat a fish someone left on the floor by the pier, and that fish being delivered by cart on a rail network.
Later in the game when you’ve accumulated mountain lore and trade lore through exploration and overworld deals, railways and elevators become available on the tech tree.