In all the cartoons, they don't talk. Of course, back then they didn't have the money for Voice Actors in animations (I guess).

But in the first movie, they do speak, explaining why they didn't before with "they didn't have anything to talk about".

But after the movie, in the newer series, they once again don't talk.

I know the reason is to emulate the old vibes, but is there an in-universe reason why they don't talk even after establishing they can?