>>53779657I think it has more to do with the fact that Ash is an ideal. He is the personification of children. Naive, kind-hearted, pure of soul, etc. Besides, is obvious Ash x Serena is the most popular ship so doubt anyone would be mad if they make it canon. In the new Anime's case, they are simply following what the Manga does. Every gen has new co-protagonists and in one way or another, these two always end up romantically involved.