I wonder why? What possible advantage would this offer? What disadvantages are there to letting it go or? Just wondering.
It's probably on the level of "If we release it, we can't possibly make money off of it ever again. If we sell it to an individual, we'll never get what it's worth. So we'll hold on to it in the hopes that someday we might again make money off of it". Either that, or they have some proprietary chemical compounds in it that they still use in other products that they don't want to reveal.