NoVa in general is extremely affluent- lots of tech, biotech, and yes, even the Federal gov't pays well (GS15s are dime-a-dozen here)! Best off are the Fed contractors...

Combine high income with very long commutes with very frequent gridlock- on par with any other metro. I think DC is in the top 5 worst driving/commuting cities?

And then top it off with the political demographic- Fed employees tend to lean a little towards the left as a whole, something that does not change with who's in 1600 Penn. Ave.

All these add to a preference toward hybrids to begin with. HOV access seals the deal. Not on the MD side of the river, though