I visited Japan a few years ago. There are regular extremely fast trains going between large cities and smaller ones. I estimated that the passenger capacity of trains stopping at one smallish city was equivalent to like 3x the passenger capacity of a major metropolitan airport in the US. From a big hub it's probably 10x that (maybe more).
The trains run very frequently, with reasonable fares. It looked to be completely sensible and fast to live in an outlying city and take the train into a larger one for work, whereas the idea of catching a commuter flight from a smaller outlying city into a major metro area in the US (or likely anywhere) is almost completely untenable -- too expensive, too time consuming, too irregular, and too much hassle.
The trains run very frequently, with reasonable fares. It looked to be completely sensible and fast to live in an outlying city and take the train into a larger one for work, whereas the idea of catching a commuter flight from a smaller outlying city into a major metro area in the US (or likely anywhere) is almost completely untenable -- too expensive, too time consuming, too irregular, and too much hassle.