Fishing has little reason to be in the game, as it detracts from the feeling of adventure and action that is the main core of the gameplay for Sea of Thieves.

Disagree with this one. You could say the same about playing music, drinking grog, dancing. They're not essential, but it's fun to have and they certainly don't hurt gameplay. SOT shouldn't become fishing simulator 2018 but it's a fun way to pass time while sailing open waters, provide food, could sell the fish. Could catch little fish or marlins or 1/1000 times you snag a whale and go for a ride. IMO the more random shit is in this game, the more open and immersive it will feel, keeps the game feeling fresh each time you go back.