I think the reason that this show is on DVD is because the rights are really cheap. I mean, they aren't the most well know property (or most beloved for that matter). Whereas Fraggles get a harder sell because their rights are much more expensive. As much as we'd all love to think things fly onto DVD, most properties sit rotting on old tapes in a box in someone's basement because of legal red tape. This also explains why Bullwinkle and Rocky are on DVD, but not Hoppity Hooper or George of the Jungle, as they are tied up with copywrites.
Also, Parents just love to buy Barney tapes to shut their little babies up instead of actually parenting in the first place. Therefore, they sell better, and the venture is well established and profitable (Unfortunately....) Fraggles seems risky, since they want to make them for a children's market, dispite the fact more adults would want them.
With that said, I don't see why anyone would have even bothered with New Zoo Revue. It's not that good a show. It has its moments, but I've seen it (on a UHF station that airs home shopping club, to fulfill it's daily allotment of Children's broadcasting) and it's pretty much better forgotten. The puppetry looked pretty ugly. I mean, I doubt any kids would want to see anything of that caliber. 'specially how frightning that Hippo looks.... Personally, I always looked at this as a cheap way to cash off of Sesame Street back in the 70's. A ripoff. Since SS did so much better in every aspect (puppetry, acting, music) it's no wonder why it's so forgotten. But if you're happy, I'm happy!