It was likely a top line revenue increasing move. The Origination/Desitnation market for New York-Buenos Aires is larger than the Origination/Destination market for Washington DC/Buenos Aires combined with the fact that you can generally charge more for non-stops vs. connecting flights (Especially in this case where your connecting flights from IAD-EWR/JFK/LGA are undesirable). A similar reasoning caused Glenn Tilton to whimper about not having an NYC hub the entire time he led United.

I did EWR-EZE (rt) in BF a month ago. Take-aways:

-They worked miracles to get the PMUA ghetto birds to look spiffy. I thought I was flying on a relatively new plane from PMCO. It's hard to believe that this plane probably had duct tape visible inside the cabin only a year ago.
-The food was ghastly. Nothing at all like PMCO catering. I was shocked. It was closer PMUA Business class catering, only worse.
-I don't have issues with most personnel at EWR except the lounge agents. They are something else, and not in a good way.