This is the biggest problem with transit outside NYC/Chicago. Those cities are surrounded by walkable suburbs that justify regional rail. Everywhere else, the surrounding suburbs were not designed at all, and it's questionably valuable running rail out to them.
I take the Silver Line to work in D.C. None of it runs through any sensibly designed area. There are a tiny handful of apartments within walking distance of any Silver Line station, and even the closest ones are separated by enormous dangerous parking lots. My commute is actually takes longer than it did back when I used to commute from a walkable New York suburb into midtown, even though the physical distance is about 40% less.
I'm pretty skeptical of the return on transit dollars in place like Seattle. It seems to me that it's simply too late to turn these places into real cities.