In the pre-Great War era, the reason wing turrets for main battery guns on dreadnoughts were abandoned was simply because of weight. While more compact machinery did play a role in keeping the size of the ships down to a manageable and cost-efficient scale, the move to centerline turrets came because turrets and barbettes for guns larger than 12 inches were simply too heavy. There was no way turrets and barbettes of that size could be safely and securely mounted away from the structural rigidity provided by the keel of the ship.
The peculiar case of the US Navy, which never deployed wing turrets on dreadnoughts, came because of self-imposed tonnage limitations during the era in which wing turrets were in use. For example, while HMS Dreadnought and the Nassau-class battleships both had full load displacements over 20,000 tons, the South Carolina-class dreadnoughts were built on predreadnought hulls that displaced up to about 17,000 tons.