Two points regarding Satellite Parking's problems at ELP:

(1) With only two ORD flights, AA probably faces greater problems trying to reaccommodate those passengers than a passenger flying to or making connections in DFW. It's a judgment call, but I can see this as a possible justification.

(2) Smaller airports need slot limitations for morning flights. At CRP, for example, WN has a 737 flight at 6:50, DL a CRJ at 6:55, AA an ERJ at 7:00, and CO a 737 at 7:20. Given that WN allows passengers on board as late as the departure time while the others (try to) close their flights 10 minutes early, all four airlines have flights boarding within 25 minutes of each other. That's a recipe for disaster at any small airport. Those flights need to be spread out over an hour instead of compressed like that.
Allowing the airlines full discretion to pick their departure times at small airports presents the choice of heinously long security lines or having extra security staff stand around the rest of the day.