Fewer sets of runways seems like it should be easier, because the runways can be set up to be parallel to each other, so planes can all come in on the same appr

Fewer sets of runways seems like it should be easier, because the runways can be set up to be parallel to each other, so planes can all come in on the same approach and land in parallel. That's how they do it in Phoenix, with three parallel runways. With more airports, you have planes all going different directions instead. Besides, it seems like it'd be better to push some of that air traffic away from the city center, and free up some extremely valuable real estate. If they'd put in some better public transit to those two airports, people would be able to get in and out of the city a lot faster. Why can't they build actual subway lines to them anyway, instead of having to make slow and crappy, special trains to them which aren't on the main lines and then require time-consuming transfers?