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.
Someone needs to tell those poor saps trying this out of Gatters. What's their name again? Flying brand new B787-9s....oh God that's so annoying, Swedish Air Shuttle or something?
OK in all seriousness, you can't market the benefits of doing something the Norwegian way whilst mentioning how much better it is than the (other) Norwegian way of doing things (!) It's a fragmented strategy, going Hell for leather for market share is one thing, but as you can see it brings problems of positioning. Once you pay for your meal and seat it's seldom bargain basement pricing anyway.