I think Boondr hit up what I was thinking, nobody there is watching the runway and it is night. I guess for me the tower is one extra layer of protection at a very unique airport (proximity to White House and other important places), and in any situation it would seem the thing to do in an airliner at night especially. It isn't very far to go over to Dulles and for the passengers sake, they could be bussed over to National. I will make it clear that I am not an airline pilot and my decision making is from a PSEL perspective, so I do not know everything that goes on as a PIC of an airliner.