Because there are no grownups on the island so they can play as they want to .
Chat with our AI personalities
The plane on which the boys were being evacuated crashed on the island during a storm and the adults (along with some of the boys) on board were killed.
Ralph stands on his head when he first realizes that they may be all alone with no grown ups on the island.
Excited because they feel that until they are inevitably rescued they can have a good time, as they are on a "good island."
because when they heard the conch being blown, they knew there was some person on the island and they weren't alone, or that they thought somebody was coming to save them
When Ralph told the assembly of boys that they were on an island, "like in a book" various boys called out.. "Like Treasure Island, Swallows and Amazons, The Coral Island." As Swallows and Amazons doesn't take place on a tropical island the other two were much more apt.