There are four reasons that a person might tell a story about someone else:

1. Trying to get help for the subject
2. Schadenfreude
3. Bolster a sense of self-importance
4. Get advice for self if the gossiper is intimately involved with the subject who might be a family member or boss or coworker.

The first three are typically destructive. The gossiper might convince themselves that they are just "trying to help" but gossip doesn't usually produce the kinds of results that the subject might need.

The last assumes that the person hearing the gossiper's story is a trustworthy friend. If the friend is not trustworthy, the story can be further spread to the gossiper's detriment.