Why should I use fabric softener?

Machine washing puts great mechanical stress on textiles, particularly natural fibers such as cotton and wool. The fibers at the fabric surface are squashed and frayed, and this condition hardens while drying the laundry in air, giving the laundry a harsh feel. Adding a liquid fabric softener to the final rinse (rinse-cycle softener) results in laundry that feels softer.[2][1]

Machine washing puts great mechanical stress on textiles, so adding a liquid fabric softener to the final rinse results in laundry that feels softer.