Besides the fact that the U.S. government wanted to keep American troops fighting overseas well-equipped and well-fed, another reason for rationing was the fact that the production of some products had to be reduced since many factories changed their peacetime production of goods marketed in the civilian market for products required by the wartime effort.
For example, silk, a fabric popular before the war in the manufacturing of women's stockings, practically disappeared fro the civilian market since all of its production was earmarked by the military to be used in the manufacturing of parachutes for military pilots, aircrews and paratroopers.