Because they can make better money elsewhere. Why slash fares and increase frequencies (which doesn't make money) when you can move the planes elsewhere and make money? It's a business, not a charity.
Just a few years ago they were making good money at ISP, even with LGA in existence right next door. I bet they could if they tried. New York area to Florida is a huge market, even after the pandemic. Hopefully after this summer trend of travel-to-outdoorsy-areas dies down they can add more ISP flights.
They just resumed ISP-BNA yesterday after quite a hiatus. I assume ISP-PBI and ISP-MCO is still going though.
Additionally they can route everyone through BWI and get them there. There are loyal WN flyers on Long Island and they probably won’t lose them.
I’m happy about ISP-BNA. The sad part though is that it gets into BNA at 8:00 PM, reducing the majority of connecting opportunities, and it may be tough to rely on O&D traffic for a flight like that. The flight out on Monday only had 70 or so pax according to LIMA’s Facebook. Hopefully those numbers increase as the flight goes on.
Your point about connecting in BWI and loyal Southwest pax on LI is correct. Some people will do anything to avoid LGA and JFK. However, there’s also a bunch of casual non-WN loyalists on the island who much prefer a nonstop flight and if those are gone they are going to non-happily make the drive or train ride to JFK or LGA.
If they are going to keep it as a late-day departure to BNA, I’d love to see MDW and/or LAS come back. ISP-MDW is Southwest 4th underserved city pair for 2020 (was #1 in 2019, I assume the slight loss was due to loss of business traffic) with around 53,000 people connecting in BWI to get there. That number would definitely increase with a nonstop flight, and more people connecting in MDW to get places. LAS would also be a great connecting spot in the winter for flights to the west coast if MDW and BWI are being hammered by storms.