Close to nil O&D traffic, very little premium traffic = perfect route for DL to operate...
Seriously though, the route is not an option for CSA anyway, because of missing long haul equipment, but considering DL`s operating costs, a high density 767 could make money seasonally from late May to August, although add. service from NYC on the route would make more sense. Menzies provides handling at rock bottom prices.
Still a beautiful city with way too many drunk US and UK tourists, unfortunately...
But where else in the world can you listen to a classical concert by young and promising musicians for as little as € 5 ?