Wing bending relief was designed and in use with the DC-4 (yes indeed folks, that far back) and its purpose was to relieve strain at the wing/fuselage and inner/outer wing attach points and allowed for lighter wing structure/higher payload. It was improved with later models of the Douglas piston line (DC-6 & DC-7) and especially the DC-7C with its much larger fuel capacity. When the jets arrived (DC-8 & 707) wing bending relief provided much larger fuel supplies to be carried and on the intercontinental models the weight of the fuel exceeded the empty weight of the aircraft for the first time.