William Golding is often quoted as saying that technology is often not as important as spirituality or physical strength. In fact, he even said in an interview that at the end when Ralph is weeping for Piggy, he really should be weeping for Simon - who is symbolic of spirtuality. Intelligence is important and valuable, but so, too, is physical strength. Only when they work in harmony with one another can real change be affected. That is perhaps where spirtuality / morality comes in. That is the key that links the two.
The boys who on Jack's side, which is an ever increasing number as the story progresses, treat Piggy with disdain. Ultimately, they kill Piggy because he tries to reason with them in chapter 11. They value Jack and his physical prowess over Piggy's intellect. The fact that Jack's tribe increases in number is evidence of the value of physical strength over mental strength. Whenever Piggy tries to speak, whether holding the conch or not, he is shouted down. Piggy represents the voice of reason and that voice is not given the chance to speak or be heard. Jack's tribe emphasizes fun and games, especially games of physical prowess and stamina - and that's where the boys gravitate.