Do you think it could be a way to introduce accents in CAS without record all the simslish voices again? Each world should have it's own accent for the local sims.
Rey from the Journey to Batuu pack has a British accent. However, they only recorded a few lines in Simlish with the voice actor. Thus, she is mostly mute if taken out of her role in the Batuu storyline and moved into a household. Removing her hidden traits allows her to talk like a normal Sim.