Too much of a good thing.
Using too much fabric softener on towels can leave a waxy, water-resistant coating on the fibers that is the opposite effect of a good towel. Would you use wax paper or a paper towel to blot water? To get your towels back to absorbency, add a quarter cup white vinegar to the rinse cycle for a few washes – without softener, ever. If you have the luxury of a clothes line, nothing beats air dried towels for a crispy, fresh feeling.