Why an uncrewed submarine still needs a sail

Why would an uncrewed undersea vehicle need a conning tower or sail?

It provides maintenance and port access while supporting taller masts and sensors without forcing the main hull close to the surface.

Two practical reasons explain the sail: maintainers may need access while the vehicle is at sea or in port, and the structure lets the hull remain deeper while carrying longer telescoping masts and intelligence sensors. It therefore supports human servicing and sensor geometry even when no crew rides the vehicle on mission. An autonomous craft may preserve familiar submarine features for different reasons.