Sometimes an idea can be so enthralling that I feel I need to tell people right away, before I even finish thinking the idea through. When I explain it, there's no context and my listener thinks I'm crazy. I'm so deep in the idea that I'm not explaining how the idea can relate to anything.
This is why stories and metaphors are effective. They give the listener a way to connect with ideas.
The more familiar a listener is to you, the more familiar they are with your ideas and the less context they need.
Context is like credibility. Sometimes it's understood, sometimes it needs to be slathered on.
The important concept it: Don't give your readers homework.