IME, this is less of a problem between legacy US hubs than legacy AA hubs. The AA hubs have substantially more population base than the US hubs. DFW-NYC, for example, is a way denser market for both O&D traffic and connecting pax than any two LUS hub pair. One DFW-NYC cancelled AA flight is going to pinch the seat count a lot harder than a CLT-PHL on average. The loads are just never as dense.

I don't commute, but I'm from DFW and have been pass riding between DFW-NYC for years. It can get brutal on AA when it goes IROP or around the holidays. However, it's nice to have the jumpseating option. Opens up AA, DL, UA, NK, and WN/AS from DAL. Usually over 40 daily weekday options from Dallas airports to NYC airports with Republic flying to both EWR and LGA from DFW. That's a nice chip to play over mainline bros when the cards are down. At worst, we always have jumpseat priority over anyone else on our metal...