Is there a reason why Poke Ball experts don’t have Poke Ball Pokemon?

So I’ve always wondered this for years, and maybe fans share the same question, and maybe fans don’t know the reason. But I just wanted to finally put it out there. Is there a reason why Poké Ball experts don’t have Poké Ball Pokémon? Kurt is only around a bunch of Slowpoke, and Karna has that teacup Pokémon, Sinistea. Why unrelated Pokémon to these characters? It just never makes sense to me. Also, even with Karna having a Voltorb and Electrode, it would actually be helpful. With Kurt, I can see him treating his Voltorb and Electrode like best buddies and totally in sync in battle and only having electric moves, and he uses them somehow to study Poké Balls. Also, I find it weird how Pokémon doesn’t know what to do with Voltorb and Electrode when they look like Poké Balls and honestly could’ve been the Pokémon mascot like Pikachu since it makes sense. Another thing that makes no sense is how come they’ve never done more Poké Ball episodes and talking about all the different ones like the Love Ball? A story with people interested in poke balls and studying them and having a Voltorb and Electrode is literally the perfect story right in front of them! Maybe they don’t want to be obvious or do stories like that, but it just doesn’t make sense how we always ask for slice-of-life or different things and then insist on focusing on the battling aspects of it and being close to your Pokémon (which I can do with or without it).