I found 4 quilt tops at a local thrift store and asked if I could take them home, finish them and re-donate them. They wanted me to pay for them, but I said I couldn't do that. I would be adding batting and backing and lots of work. So they let me take them home. In a few months I had them back at the store. The tops were all new, but not fancy. Just 6 in. squares sewn together. But I hope they keep someone warm.
Another quilt top I found another time was very poorly sewn. Also 6 in. squares, but I just wanted to go to the poor lady's house and fix the tension on her machine. I had to take out whole rows and resew. I should have taken the entire thing apart. An Amish friend ended up putting the ties on it and remarked how poorly it was sewn. She hadn't seen it before I "fixed" it. It was then donated.
I think a lot of these quilts you find at thrift stores, especially the unfinished ones, were donated after the maker passed away before finishing them. The family doesn't want to/doesn't know to finish them.