I believe that started when people were doing more handquilting (just my opinion). 32 yrs ago I made a quilt for my daughter. I slapped 2 Kmart sheets together and tied them. It was HARD to get the needle to go in, but I did it. She STILL has that quilt --- and it was dragged everywhere she went.........camping, sleepovers, etc. So, GO AHEAD and use sheets for quilts that are NOT going to be in shows. The QP at quilt shows may not accept them....but who knows!!! Oh -- I use sheets from thrift stores to practice on my longarm............LOL and the longarm quilting machine DOES quilt them just fine. But if I were to be putting them on a quilt, I would trim all selveges off and all hems.......those make the quilt backing tweak funny