Final answer:
Jack is important to the group in 'Lord of the Flies' due to his leadership in survival, while Piggy is seen as useless because his intellectual contributions clash with the boys' immediate, primal needs.
Step-by-step explanation:
The characters of Jack and Piggy in William Golding's 'Lord of the Flies' serve as representations of fundamental human impulses and societal roles. Jack is important to the group because he embodies the primal instinct for power and survival. His ability to hunt and provide meat wins him the respect and fear of the other boys, making him a strong leader in a situation where the traditional adult-imposed order has collapsed.
On the other hand, Piggy is often perceived as useless to the group, largely because his physical weaknesses and intellectual approach contrast sharply with the boys' savage instincts and immediate needs. However, this perception misses the essential contributions Piggy makes through his knowledge and rational thinking, which, if given proper consideration, could guide the group towards a more civilized and structured society.