IAD is always going to have more flying then either DCA or BWI since it’s the hub.

for example in April. Pairing ops by departure airport

320:
IAD-218
DCA-129
BWI-69

737:
IAD-587
DCA-129
BWI-112

getting from DCA to IAD is not hard. Metro if you have the time or Uber/Taxi if you don’t.