Hey guys! Im currently rewatching the Indigo League for like the 50th time, but I got to the episode where Ash and the gang stumble upon Bill's lighthouse. During their talk with Bill he discusses a higher purpose to studying Pokémon and you can tell this makes Ash internally question his journey. Then Bill tells them about a Pokémon hes been communicating with briefly over the ocean and says its a one of a kind Pokémon, it has no friends or family and is possibly the biggest Pokémon in the world. Bill says he hopes to one day meet the Pokémon hes been communicating with, then Ash asks him if hes going to try and catch it if he does. Bills response to this is "Why would I need to capture it? Meeting it would be enough for me. Just a chance to study it would make my long wait worthwhile." Right before they see what looks like a silhouette of a Dragonite coming towards them.
My though is, Ash is certainly the most lucky Pokémon trainer in this universe, he encounters basically every single legendary Pokémon there is to encounter and all just by chance. Yet, he never tries to capture any of them, at least within this series and in the movies Pokemon: The First Movie, Pokémon: Mewtwo Strikes Back, Pokemon: 2000, Pokemon 3, Pokemon 4ever. (If you consider the movies to be the same cinematic universe as the TV show.) With the only exception being Meltan which us technically a Mythical Pokémon.
After hearing what Bill had to say about one of a kind Pokémon, do you think that's the main reason why Ash never tries to catch any of these incredible Pokémon he encounters? In some cases ita obvious that catching the Pokémon would disturb the natural balance of things, however in others catching the Pokémon would have no impact on the World in a negative way. Do you think that he considers his interaction with them and his opportunity to fight alongside them against people who are trying to capture them enough. Like Bill said, just getting to study them and encounter them at all is enough for him. Most trainers will never even catch a glimpse of a legendary Pokémon, like for example at the begining of Pokémon 4Ever when they are on the boat and they see Suicune just chilling in the forest before he runs away. Like just that encounter would have been a legend that passed down generation to generation and theres a lot of folks in the Pokèmon universe who never even really knew for sure many of these legendary Pokémon existed until Ash's first hand encounters with them.
I personally think its a combination of what he learned from Bill, plus his overall shift, from being obsessed with becoming the Pokémon master/wanting to catch any and every Pokémon so he can be better than Gary, to him learning much about the way Pokémon and humans co-existing. The good and bad sides of it, and his general admiration for Pokémon and how incredible they can be. He shows a lot of respect towards them and in return they show respect back to him. I think the relationship he builds with many of them out of mutual respect means more to him than beating capturing and owning them.