Of course it will be useless for you if you already have some understanding of the UNIX heritage. As with all metaphors, its value is for people who know very little about the topic, in that it helps them relating the topic to something which they're already familiar with.
For someone without a previous knowledge in the history of UNIX, the metaphor provides a mental map to navigate intuitively what was perceived as an impenetrable technical mess. It can provide the idea that there is a heritage of branching from a common origin, a sense of what are the main branches, their relative antiquity and importance.
Moreover, it's funny and light-hearted. Why does everything has to have a practical purpose?