Language exists for people to talk to one another.
Ken laughs. Yohji purrs. Aya growls and grumps. Omi chirps. In the shop, it's easy. A word or two, here and there. A quick, gruff threat. They don't have to speak, although Omi does. He likes to fill up the space. Words are just sounds, comforting not communicating.
On a mission they don't have to speak. Words will just get in the way. But Omi still chirps, the sound harder, faster. Aya's harsh growl is all they need to hear. Yohji's languid voice fills the communicator like cigarette smoke. And Ken laughs a dry, humorless laugh.
Speaking is not communication.