A sailor, looking towards the back of the boat:
- There's an incoming boat !
- From where ?
- From the left !
Is it the left of the sailor, or is it the left of the vessel ?
- There's an incoming boat !
- From where ?
- From the left !
Is it the left of the sailor, or is it the left of the vessel ?
So it’s not actually achieving anything. You could just say left always refers to the ship’s left.
What you achieve is a new set of coordinates relative to the vessel. You are going north, sitting on the port, with a glass of wine in your right hand, instead of going up and sitting on the left.
If you use left and right for the ship, you wouldn't be able to use personal left and right without risking ambiguity. You'd just be trading one convenience for the other.