>>56616689I'm actually not sure. Pokemon is not a show that grows with its audience, and since that's the case Ash should have gone a long time ago and shown up in the journeys of others, same with Gary. Like the OG red ranger. Every season reintroduces the concept of Pokemon and that makes more sense with a different protag every time they do that. It does not make sense to have ash Pokedex a koffing, he saw a koffing basically every day of his life for a time. That's exclusively for the benefit of the audience, who wasn't there, and it makes more sense to have a character who learns alongside the audience. At some point you have to let Ash be a veteran trainer, and at that point he's not relatable to the young children that are the target audience.
At the same time, nerds do not like change and Japanese nerds REALLY don't. Look at Goku, he was clearly meant to pass the torch to Gohan after the Cell Games and Japan was not havin' it. That's how it is with Ash. Could he have finally gotten his championship, looked across to his younger opponent and said "don't be sad, you did well. I've been in your shoes before. Don't stop trying, don't let your friends down, don't give up on yourself, because they won't. Who knows? You might be the very best!", and then he gives him his hat, we pass the torch, Ash gets to be the very best like no one ever was, and the show runners get to write the same show again for a new audience. Wrinse and repeat every other generation, keep the hat as a motif. But there'd have been hell. Lose-lose situation. Instead Ash got to re-learn lessons he'd already learned, rediscover pokemon he'd already discovered, never seeming to learn or grow because of he did he might change, and change bad.
All that to say, why didn't they? Because the only winning move was not to, just wait it out until the old guard changes and a torch can be passed or we get Pokemon Super.