emphasis added...
That works if your business plan does not depend on having any repeat customers.
True, but they will keep the fares down for routes to Florida, which means US would have to undercut WN to entice people to fly ISP-CLT-FLL/TPA/etc vs ISP-FLL/TPA/etc n/s on WN. Of course, US would have more connecting opportunites in CLT than just Florida, but I imagine that Florida accounts for a big portion of the traffic from ISP. Plus, we can route them through PHL.
That works if your business plan does not depend on having any repeat customers.