The Vienna Metro station is the last station on the Orange line. It is meant to be a park & ride station for commuters from Fairfax, Centreville, Gainesville, etc. so those individuals don't drive all the way into the District. Same for Franconia/Springfield, New Carollton, Shady Grove, etc. tufsu1 is correct in that many of the stations closer to town have enormous TOD's attached to them (e.g., Ballston, Pentagon City). Problem is those neighborhoods are not cheap to live in.
Unrelated question: is it physically possible to build underground rail in Florida?