It’s one type of animation pretending to look like another type of animation. Why not just hand draw the darn thing? Guess I’ve seen it used on one too many cheap looking shows.
And it’s not impossible to merge 2D and 3D animation, like hand-drawing characters and CG-ing ships. It’s not ideal, but some shows like Netflix’s Voltron reboot have done a great job with it imo.
Voltron is such a good show. Much better than Rebels anyway.