The red eye project started with an outcome that no one really wanted with the goal of increasing it's value by taking some out of circulation.
Because of the popularity of the thread and the number of people involved, the once rather common pet now has a very nice trade value.
Once you hoard something, you get attached to it. The things that you didn't like, you don't notice so much now and you can point out things you like about it. There is always someone out there that adores that totally unwanted pet enough to hoard it. I believe there's a couple of people that hoard rainbow drafts to name an example. At one point, warrior cats couldn't be given away because they were so unwanted- anyone could get many of them any time they wanted so why make more?
Now they are rare. This could be because people deleted the extras in droves when Tess made a post about the number of pets in CS waaaaayy back in November when limits were made but who is to say for sure.