Steve points out why conversations are necessary, and I would add, not just the electronic or text communication that passes off for communication these days.
However, in my view, conversations are also the basic building blocks of that elusive quality called trust.
Ongoing conversation between people at work serve at least two important functions:
1. They help enhance our sense of worth and life by being an accepted and contributing part of a community
2. They give people cues as to how our life is going
The first is literally a preventive function. By being included--or "part of the conversation"--our need to belong is met, at least in part. When our most basic needs are being satisfied, we feel more satisfied.
The second provides a chance to ring the alarm in the minds of our colleagues. If something is wrong, they may very well sense it and listen for the level of severity. When we've established relationships through conversation, we're more likely to believe there is help in the form of those around us.
In fact if you are a service provider (whether internal or external) and want to move into the space that David Maister calls being a "Trusted Advisor" then you should read his book. It tells you that technical skills are not enough to be called a trusted advisor. If you want to move from a subject matter expert to a trusted advisor then the key is interpersonal relationships. It talks about being upfront with your clients and not to focus on just yourself or your skills or lack thereof. It also means confronting the client sometimes and the skill of conversations, specially difficult conversations, is key to it.