Why naval auxiliaries are hard to build jointly

Why is there not more international cooperation on naval auxiliaries?

National operating needs and ship sizes differ, while domestic industrial policy gives navies a strong incentive to order their own designs.

Britain's split from the Horizon frigate project in pursuit of a larger, more independent Type 45 design illustrates the problem. In a joint auxiliary programme, the United States may need a very large hull, Britain or Italy a large one, and other fleets medium or small ships. A single design can therefore become a compromise that satisfies no participant's operating requirement. Even similar tanker designs struggle to gain partners when governments want orders to support their own industries.