I like to remind my European friends that this is what the US looks like placed on top of Europe: https://i.imgur.com/HkRZfKd.png
Its not a perfect illustration but it drives home the point.
And how come China does a much better job than the US while they have the same surface area? Why aren't you overlapping those two maps?
But as the city transitioned from a manufacturing / industry / banking to a service economy, the jobs spread out. If your primary business need is an office park to answer phones or crunch numbers or move lightweight product, property in the suburbs is cheaper. So now you have a situation where someone lives in the two o'clock suburb and their job is in the three o'clock suburb... And there's no bus from here to there, there's a bus from two o'clock to the center and back out to three.
... or they could use a car (carpool or owned), which will cut the travel time by a third.
Retooling to the modern needs is going to really goose the cost (especially since nobody wants to tear down the current model at the same time; the people who rely on it do rely on it to get to their jobs and back, still; their job isn't heavy industry anymore, but people still work downtown!).