I don't think it's a status symbol for most people.  Most, I suspect, either don't have many options, or don't realize what options they do have.  And I suspect you're right about convenience.

If you live twenty or thirty miles out of DC, you don't really have much to choose from, unless you live near a VRE or MARC station.  And there are all of -- what, four or five between here and Richmond?  As you said, it's drive or go nowhere for most.  Even in the close suburbs, the train coverage can be pretty pitiful.  Building that Purple Line around the Beltway would help a great deal in grabbing some outer suburbs and cutting congestion downtown.  (I'll even get on-board with your dumb Dulles Line if we can do that. ;)

People will carpool when gas gets too expensive to drive individually.  Many in my office are starting to do it now.  Then they'll trade their SUVs for midsize cars or (gasp!) compacts.  We'll be a nation of Dirty Fucking Hippies before you know it.

And it's not places like DC that we really have to worry about right now.  DC's got too much money for its own good anyway.  It's out in the Provinces where people are getting hammered.

Be nice to America. Or we'll bring democracy to your country.