The word "rum" is used over 70 times in Treasure Island. The only fun thing the pirates ever do together is drink. This reliance on alcohol also proves to be their undoing. Because they are all stone drunk their first night on the island, no one notices when Ben Gunn sneaks up and kills one of them. And who wants to imitate both Billy Bones and Israel Hands, so desperate for a shot of hard liquor after their injuries that they will promise Jim anything to get it? Rum becomes another means of symbolizing the moral weakness and lack of discipline among the pirates.
Long John Silver differs from the other pirates in that he recognizes that drinking too much rum wastes money. His views on alcohol become another tool of characterization to show his unusual discipline and restraint.
Alcohol is the root of all of the pirates' problems in defending their territory and organizing attacks on Captain Smollett and the rest of the ship's leadership.