When using technology, usually there is inherent trust that the outcome is correct because it has been tested before going to market.
With competition, time-to-market is squeezed. We have seen examples of vehicle recall for fixing certain faults. Even worst, other factors like insufficient training, lack of comprehensive operation instruction could cause tragedy or fatality.
In the illustration, GPS infrastructure is proven but the map data might not be updated or the software to map the GPS signal to the location could have fault. A dual GPSs could mitigate an incorrect navigation if the impact due to incorrect route is significant.
That said, the entire principle gets back to risk management – what measures can be controlled to reduce likelihood and what does not.