If I had to guess, it's because they don't want any one team or interpretation of the characters to get TOO popular.
These are evergreen characters. Part of their strength is that they can do multiple different versions of them, and they can all be fairly legitimate. But, if one version becomes TOO popular, then suddenly fans complain when they get written some other way. They complain that they act "out of character", even if their characterization in another show is supposed to be different. They get stuck making these characters act in a certain way. They probably like having more flexibility than that. They most likely don't want these version of the characters to be seen as the "definitive" version of the characters.
There's also that they probably just don't want the creatives to get too much bargaining power. If the show goes on for years and years, then suddenly you might get voice actors that want raises or animators that want more money. It's hard to replace them, and becomes a very public spectacle when you do. Disney most likely doesn't want a bunch of projects that are like the Simpsons, where the voice actors are paid millions because they're iconic, and it'd be a nightmare to replace them, just from a public relations standpoint. It's probably in their best interest to make a show that's reasonably popular, sell some toys, then get out before it becomes a big cultural touchstone. People will probably remember this show for years, and that's good enough. They probably don't want it to go on for decades.
And then there's streaming. I don't know how everyone's contracts were written concerning streaming, but, given how big it's become just in the past year, chances are DIsney might just want to do some new things concerning streaming, contract wise. And, it's easier to write new contracts for a new show than try and change contracts for a currently running show. *shrug* Might have suffered from just being around during the cusp of the broadcast-streaming changeover.
And like Sabrblade said, it seems to be a fairly common thing for the Disney Channel in general. Maybe for reasons listed above, maybe to just make room for new shows and to finish things off before the show gets stale and less popular/profitable for the channel. Maybe for all the above. Maybe none. It could be the creators of the show just wanted to do new projects, too. No one likes being typecast.
Edited by ZakuConvoy, 17 March 2021 - 10:15 AM.