>>47301515The same reason why Paul and Alain don't show up again. This is Ash's story and it's all centered around him.
Yeah, Pokemon is the rare kodomo anime that would actually work as a semi shounen with rival arcs and stuff but the animators make sure it never steers that way too much since they need to keep it as an eternal advertisement to the Japanese child audience.
Gary is an outlier since they've turned him into a pastiche for game canon Blue at this point instead of the loosely inspired Blue OC he used to be.
