Actually you couldn’t be more wrong on that, SWF is no further from down Town NY in terms of travel time than JFK, you’ll be through homeland security within 15 mins and flights from DUB & SNN have pre clearance so its just like getting off a domestic flight, collect bags and you are gone, there is a shuttle bus outside the terminal (often a couple of them) to take you down town in 60-90 minutes it waits for the flights if late for any reason.
PVD is 60 minutes and $65 by uber to BOS Logan but there is a huge population all the way down the coast from BOS to NYC, a lot of Irish families and of course the is the not so small matter of APD which is €3 from Ireland or BFS but closer to £90 from EDI
SWF is going double daily starting in April from Dublin, if the SNP go back on their promise to half APD i think Norwegian will walk away from the US or go very seasonal.
Going into KBOS or KJFK would add significant handling costs and crew delays, plus its a market already served, so this is in the main new volume attracted by low fares, the spend on seat allocation and pre booked meals is very high as you would expect on a 7 hour flight.