Just to nit-pick, this is not the reason why AA status members don't get domestic lounge access. It's because AA has a profitable (?) club membership scheme.
And also that if AA allowed in their own Emeralds and Sapphires, the clubs would be overrun and unusable. You think the Pier F is crowded? Imagine an Admirals Club in Philadelphia or Miami if ExecPlats and Plats could use it on every itinerary.