identification, not communication
A logo like a person's name, doesn't need to tell you a life story, it's sole purpose is to help you identify the brand. As with a name, after years of shared experiences, the sight of a logo (similar to the mention of a name,) should bring back memories associated with the brand, whether pleasant or unpleasant.
Masters of design leverage this knowledge to create icons that are simple, easy to recognize and easy to remember. They understand that after years of association, all the memories of your experience will be stored in or triggered by that simple symbol.