NYC and DC don't really project to other metros. Travel to and from Penn Station vs the airports is a non-trivial consideration to passengers. It is expensive or time consuming or a PITA to travel to JFK/LGA/EWR on public transit with a bag. I lived in Brooklyn and made the NYC/DC commute 15 or so times a year for many years and that was a significant issue for me, it just wasn't cost or time effective to fly in _NYC_.
I now live in Maine and wouldn't consider for a second taking the train to NYC. I'll fly out of PWM or, if I want flexibility, drive there. There is a non-stop bus that I'd prefer, too.
It helps that due to a mix of incompetence and lack of support from the governor‘s office that there is no direct train link through Boston that a train from Maine might use to get to NYC.
I now live in Maine and wouldn't consider for a second taking the train to NYC. I'll fly out of PWM or, if I want flexibility, drive there. There is a non-stop bus that I'd prefer, too.