True, but I think ISP and MKE are a little different.
Long Island residents can easily drive to LGA/JFK/EWR. With Southwest being in bed with the Islip government and having the airport by its cajones, Delta couldn't truly compete in terms of ticket prices. Plus, Delta's lack of advertising (in all markets) doesn't help. Most people didn't even know they could fly to Boston on Big Sky.
MKE area residents don't have much to choose from.