The Pokemon anime... with Ash(not all of them have Ash) is weird because it's taking the stories from the games and warping them to use Ash as the MC when it's a story written for a different character. And this is part of the non-aging thing... it's a new, young PoV... because it's a story meant for a different new young protagonist... who is NOT Ash. Like... Dawn.... she was the MC in her story(the video games Pokemon Diamond and Pearl)... not Ash. But the anime warped the story to make her Ash's sidekick.
In part because Goku is ACTUALLY the main character in his stories. Also, in the first episode of the original Dragon Ball, Goku is a little kid who doesn't know what the word "marriage" means and his future wife actually tricks him into agreeing to marry her because of that. Granted Chi-chi wasn't a bad wife, and decades(both in and out of universe) later Goku is a grandfather.
Yeah, some episodes don't even have Goku in them. But most do, and all have a defined point in Goku's life when they happen.