Nanite was/is optimized for "next gen consoles" like the PS5 which has now become the current gen consoles. Things like direct NVMe-to-GPU asset loading, bypassing both the CPU and OS, is still early beta tech on PC.
And it's also completely unneeded as you can see when running Forsaken or Ratchet & Clank on PC without it.
Those are not games that fully utilize the PS5's NVMe-to-GPU asset loading tech. Things like actually flying over a giant open world map without merely teleporting.