interesting question i have to check and see. usa still has an important cotton crop.
fabric softener coats the cotton decreasing it it's inherent cotton-y qualities.
air movement shakes the fibers and prevents them from stiffening, the same way the dryer does, but it smells better, doesn't it? the fibers are actually absorbing the smells of the grass, flowers etc. if there were bad smells, they would absors those too.