One of the rules from airline economics is "don't overfly your hubs" as in
[United's President [Scott Kirby observed about their domestic hubs that “It’s rare we’re overflying our own hubs.”
more here
Basically, never fly nonstop by bypassing a hub.
PHL is obviously a hub. So sometimes we consider WAS-PHL-NYP super expresses. But then BAL and WIL have wicked slow speed approaches--if the geometry hands you lemons, you gotta make lemonade (and stop).
In the studies thread, F-Line has argued that even if you had the money to straighten BAL and WIL enough to make them worth zipping through, you would probably still want to stop.
But we won't be there (rebuilt WIL & BAL) within the useful life of even the Acela-2