Because of the annual Washington Post Peeps Show.
I was a little disappointed with this year's results (two "Man on a Wire"? Edward Hopper?) but it was still fun to look at. My favorites are Gitmo (#6 with the Peep being waterboarded) and the classic DC tourist scenario "Peep to the Right" (#30). Extra points because this one was done by a bunch of economists:
Peep to the Right by the staff of the Office of Trade Policy and Analysis. "You really know you've become a true Washingtonian when you start to get irritated when tourists stand on the left side of the escalator," writes office diorama team leader Morgan Barr, an international economist. "We had so much fun with this, adding all the little Metro details and making angry commuter peeps."
I get annoyed when people stand on the right side of the escalator, but nobody believes me when I tell them it is common courtesy to stand on the left.
Because we drive on the other side of the road here, all these things are reversed.