Why would anyone throw away good, clean, insect free material? Maybe it's not up to your standards. Maybe you would never buy the material in the first place. But, there are so many people out there who don't have much and would love to have something to keep them warm and would be beautiful to them. Homeless for sure. Animal shelters for sure. They don't care if the quilt isn't good enough to put in a quilt show. They only care that it's warm and it's theirs. It will be beautiful to them.
I've found that quilting is for the middle to upper class who has disposable money. If I want material I have to eliminate something else, usually food, so I can afford to make another quilt. Mine aren't good enough to sell - seams don't match and I tie most of mine because I just can't seem to get the stitch-in-the-ditch down pat. But they are beautiful to me and seem to be to those I give them to. One church group here in FL uses donated sheets for the backing.
So please don't throw good quilt tops away. Find someone who would love to finish it and find a home for it. :-)