You're looking at the very rare long distance journeys. People don't travel from Paris to Marseille (400 miles) any more than people travel from Washington to B

You're looking at the very rare long distance journeys. People don't travel from Paris to Marseille (400 miles) any more than people travel from Washington to Boston (400 miles). They typically would travel from Paris to Athens by jumping on a plane, just like you'd get a plane from New York to Houston (about the same distance) Compare public transport in the Berlin metro area (6 million, 500 per square mile) with the bay area (7 million, 1100 per square mile), or the Rhine-Main region (5 million, 1000 per square mile)