A map changes when you ask how someone actually moves through it. Two places that look close in a straight line may be days apart because of mountains, marsh, water, borders, or roads that take the long way around.
Plotting routes early helps reveal where settlements, bridges, inns, ports, and chokepoints make sense. It also creates natural places for stories to happen.
Keep the first route layer light and editable. Use notes for uncertainty, alternate paths, and travel conditions, then strengthen the lines that survive the planning pass.