Another way to look at this is risk assessment and mitigation. Identity the all major risks; grounding, collision, allision with an nav aid etc.
What are the chances of grounding, collision or allision ect being caused by a navigation error, as compared with other possible scenarios? For example knowing where the vessel is but losing control? Or by failure to maintain a lookout?
Taking steps to mitigate the risk of loss of position information when navigating by eye and radar at the expense of increasing the risks of other hazards doesn’t make sense.
One person in the wheelhouse has limited resources to mitigate risks from all hazards no matter how you slice it.