The first episode of the Pokémon series begins by saying that Ash can only now get his Pokémon License, and you have to be at least 10 years old to become a Pokémon Trainer and get a Pokemon from Prof. Oak. The question is: in the world of the Pokémon anime, why it is limited to only those 10 or over? In the games, you can see even kids have Pokémon and invite you to battle.
This returns in the Advanced series where Max, despite having great knowledge, can't be a Pokémon trainer, and Bonnie in the XY series wants her brother to keep Dedenne for her until she's grown up.
Though you can say that 10 is the "age of responsibility" in the Pokémon world, it's very hard to say that. In our world, 10-year-olds are literally kids, and to say that it is the "age of responsibility" would be a joke, especially with Ash's behavior.
And I'm not looking for an answer like "it's a kid show", but a reasonable answer to the anime plot.