Even ghosts were once part of the real world, and the Homeloss, which plunged into Subspace a century ago, however terrifying it may now be, was crafted by the artisans of the real world, just like Captain Duncan, who was once a man before becoming a shadow in Subspace.
For the ordinary sailor, everything related to the Homeloss must inevitably be shrouded in a veil of "curse" and "mystery," as if the terrifying ghost pirate captain had sprung directly from Subspace itself, with no one considering whether a natural disaster roaming the Endless Sea might have personal likes and dislikes, or interpersonal relationships. Many people's image of "Captain Duncan" is like a symbolic natural phenomenon—its existence alone is accepted, without the need to trace its origins.
Fear builds high walls in the hearts of mortals, making them subconsciously avoid thinking about what details might lie beyond those walls.