Part of the company culture is how and to what quality employees communicate with each other. If there is no defined framework for the different channels and no expected norms of behavior, then everyone can act at their own discretion. This is problematic, for example, if someone needs a quick answer, but they don't indicate this anywhere to the recipient, but it's not important and they think the answer is right for them.
Internal communication also affects external communication, so it doesn't matter how much the company manager has paid attention to this. If you manage to formulate such expectations well, they become accountable and the manager saves himself a lot of nervousness.