While the chief offender is Palpitoad, and by extension every member of Ash's team besides the big 3 (pika, sni, miju) this also applies to cast pokemon as well. Should the writers even bother giving Ash these pokemon if he barely ever uses them? There really wouldn't have been much difference if Leavanny, boldore, and palpitoad's battles got stolen by the big 3 and those 3 never getting caught.