Warner had some level of ownership in the company that manufactured the snapper cases. That's why they've used them for so long. I believe that relationship is over now, which is why you're seeing new releases in keepcases.

Warner is probably my favorite studio when it comes to DVDs. Their releases are consistently reference-quality, and as Patrick says, their re-releases offer genuine improvements over the original disc. The Good Fellas remaster is gorgeous. One of those DVDs that makes my DLP projector look like it's projecting film.