You're not wrong. However you look to the wrong entity for change. The FAA isn't there to determine if that arrival should have 44 seats or 440.
You might make a convincing argument they should, but they don't. The market demands high frequency to a variety of destinations that won't support a 767. Until that changes or local regulation changes it the FAA is along for the ride. That said, I don't know as I want the FAA telling the airlines what size or frequency of equipment (and thus destinations) they can fly. Doing so would effectively return us pre-1978.