Denon had a player, the DN-961FA, that didn’t require their cases but the cases provided extra protection so that the operator didn’t need to worry about handling the CD by the edges or with clean hands. Denon also had a system that used a barcode like label on the spindle of the case that would cue the CD to only that number cut so the operator could put the cased CD in the machine and not worry about selecting the wrong cut.And the Denon required a machine specific casing that held the CD. Added cost, but it was a useful system. The Denon's were the least prone to hitting the wrong cut.