I don't think "over washing & dryer drying" is the answer.......grandma didn't wash her Quilts often, nor did she have a dryer.......
i think fabrics she used were mostly recycled from other things....curtains, aprons, clothing....and she usually used muslin for the back....personally I do too...when washed, it is soft as a marshmallow(good quality muslin).
dont know for sure, but maybe the fabrics were manufactured differently too...probably not as many chemicals......
and it seems true, hand quilting is softer.....