Inanity above aside the answers is fairly clear. Let me start by saying this akin to asking why does Yogi Bear live like a bear when he's clearly an intelligent, talking creature that matches humans in intelligence. The answer, verily, is very simple he's a bear.
Verily this is overthinking a little too much on what is a series made for children. If I recall I saw a guy on Twitter throw a tantrum because Thomas the Tank Engine had dark undertones or such nonsense, I don't particularly know what he wrote because he deleted it but the responses were there.
The series makes it very open that Pokémon don't exist as people. All forms of Pokémon media point this out, Arceus, the latest entry, has over 18 uses of the phrase "people and Pokémon" and only 3 of "humans and Pokémon" making it in clear terms that there's an obvious divide between the two.
Pokémon are also portrayed as being pet like when domesticated. This is what Professor Oak told us all the way back in Gen I when introducing us to the world of Pokémon. There's a lot that could be written about the domesticat portrayal of Pokémon and how it parallels that of real domesticated animals but it would be very long. Verily it will do well with one example and that is of what HGSS has following Pokémon do. They do things like sniff at the floor, eat random things off the ground and even chew on your shoes. Apparently all Pokémon can bark. It showcases that the series clearly wants you to think of a Pokémon as a pet in very open terms.
There's also the portrayal of a Pokémon as a wild creature which would be way too long to type. I will simply say just play New Pokémon Snap.
All in all the series makes it clear that the perception of Pokémon intelligence doesn't amount to much like Yogi Bear, at the end of the day Yogi is meant to be a bear and at the end of the day a Pokémon is a wild creature that doubles as your magical battle pet, not a person.
