Because of the the obstructions to the North (Rosslyn) and the Mall Complex (necessitating an immediate turn to the northwest). We sat for over 90 minutes back in late August waiting for the traffic to clear up for an opposite direction departure (regular arrivals / departures were on Runway 1). We could not accept 1 owing limitations. Suffice it to say, those obstructions don't exist on the departure end of 19.

In talking to a friend who is a dispatcher, we had a bad trio of issues: 1) winds calm, 2) heavy fuel and passenger/baggage load, and 3) high morning temperatures.

You see this also at SAN when heavies (A350s, 777s etc) have to wait for a break in traffic to depart on Rwy 27 when regular arrivals/departures are using 9.