CORs are very useful when the required distance exceeds the length that can be covered with copper-based wiring. Then the conversion into optical makes sense.
An example is shown below. Here the device-under-test (DUT) had to be connected to a FireMatrix system (9 bus) with the DUT located within an EMI Testing Chamber. The distance was too much to be covered with copper wiring. Additionally, the requirement was that the media converter needed to be very close to the DUT and had to be within the test chamber, requiring the CORs to leave no EMI footprint and be battery powered.
So DapTechnology built a regular triple-bus-COR, the corresponding triple-bus-EMI-COR and all necessary harnesses.