Sometimes the softness of fabric is dictated by the type--and amount--of sizing that the manufacturer uses. Sizing (and products like Best Press) can affect my breathing and I almost always will wet down (rinse) the fabric I want to use in the hottest water I can stand, and then throw in the dryer. Sometimes the water remains almost clear and other times it becomes very cloudy--almost like very thin starch.
The exception to this is when I am using donated scraps. As soon as I start pressing seams I can tell if there is unwashed or treated fabric in the mix.
I agree with Lee in Richmond, that many solids--especially the Konas--often have a coarser and looser weave. I wish I could find solid fabrics that have the same thread count. I always preshrink them, which seems to tighten up the weave a bit. I have also learned to cut slightly off grain which seems to help with the raveling.