Here's why:
* Limited popularity: While Sonic Underground had its fanbase, it wasn't a massive commercial success like the Sonic the Hedgehog games and other series.
* Outdated style: The animation style and story elements of Sonic Underground feel very much of the 90s. Modern audiences might find it dated.
* Different creative direction: Sonic the Hedgehog has undergone a significant creative evolution since Sonic Underground, focusing more on action, adventure, and speed. A revival would likely need to fit into this modern context.
* Licensing and rights: Licensing and rights agreements for Sonic characters can be complex, and bringing back a series from the past would require extensive negotiation.
While there's always a chance for nostalgia-driven revivals, the factors above make it a difficult proposition.
However, elements of Sonic Underground have been incorporated into other Sonic media:
* Characters: Manic and Sonia, Sonic's siblings from the show, have appeared in comics and video games.
* Music: The iconic theme song and other musical pieces from Sonic Underground are sometimes referenced in other Sonic media.
While we may not see a full-fledged return of Sonic Underground, its legacy continues to influence the Sonic franchise.