One thing everyone must realize is that a full airplane or half full (no matter the size) does not neccessarily mean the route is profitable. The factor that DAL is mostly concerned about is yield. If the price of the ticket vs the cost of the seat is not in proportion then the yield is low or non existent and the route does not work for DAL.
If I'Falls and Dubuque produce low yields then DAL will pull the flight. Please do not associate the number of bums in the seat to a profitable flight. That will always lead to erroneous numbers.