Gossip is a key social skill that helps ensure our healthy integration into human society. 

Gossiping with somebody is a way of bringing people closer within your social group, checking that they share your views, and bonding over shared positions and judgements. The people you gossip most with, therefore, are the ones with whom you're the closest.

Spreading rumors about a close friend doesn’t bring you closer but it leads you up the social ladder by taking somebody else down. Gossip can be greatly detrimental, but it also allows nonphysical competition and displays of power.

Gossip on celebrities is largely constructed of narratives, with arcs and patterns — the swift rise, the first fall, the redemption. According to this theory, we love gossip because it ties into our human innate fascination with storytelling.

Stories often have a moral component that provides us with patterns of behavior, develop and expand our attention, bond an audience, and let us play. Storytelling is also a good way to attract mates.