What are the various jobs assigned to the boys? Why dont the boys do their jobs?

The boys' main job was to build the shelters, while Jack and his hunters were searching for food. Unfortunately, Ralph, Piggy and Simon are the only boys who set to finish their task. The other boys are too busy playing and having fun. 

“They’re hopeless. The older ones aren’t much better. D’you see? All day I’ve been working with Simon. No one else. They’re off bathing, or eating, or playing.”