Even within businesses, people with different skill sets need to be able to communicate effectively with one another; engineers need to communicate with lawyers; mechanics with accountants; sales people with managers and executives.
People with different skill sets, from my experience, have a hard time communicating the specifications of their respective roles to one another due to the lack of understanding of each others roles. It is very important to not only communicate clearly and but to also have a grasp what what the other person's role is and make it easier for them to understand the topic or problem at hand.