Why communicate?
Companies and organizations stand by their goals. Today activities are summarized is a mission. Such a mission has no value when not being exposed.
Companies and organization do something: they deliver a product or a service. And for that product or service they look for customers. Communication is one of the most import aspects by selling these activities.
Today marketing and sales are not everything. There's also competion on the labour market. A specific communication, for example with the aim to generate (free) publicity to strengthen company image, is an important contribution.
Where companies and organizations stands for and what they do or offer, it all comes together in an image the way the outside world is looking at them. That image is a valuable property. And at the same time it's a very vulnerable property. Damage to image and/or reputation is not easily repaired. In this field: it's better to prevent then to cure.