The nature of the (corporate) beast that is an International (toy) corporation like Hasbro.

Like... most of the lower levels of Hasbro that deal with Hasbro product creation want to relook at Beast Wars (according to the last 3 years of BotCon panels - due to the "cult" popularity within the collector community), but the people at the top of the food chain (who decide on the direction of the brand as a whole) haven't given them approval for a full series, or a range within a series... because they would be prioritising concepts & series that are assessed as being more profitable (to the uncommitted consumers who buy most of their products).
If Hasbro did a small-quantity, collector-focused toy range (like Matty Collector, or even TakaraTomy), we could see more of these "fan favourites".
(I doubt that's going to happen, with all the money they make from "cookie cutter" mainstream concepts - centered around the same specific characters and settings each time.)