When you read a story about an individual, you relate to that character. You feel that person's struggle. You want them to get what they desire as much as they do. But in doing so, it isolates you from humanity.
Compare that to a story where several people all have a common goal. They operate under a shared struggle, which unites and bonds them. As a reader, these stories promote unity, teamwork, and compassion. They make the readers want to see groups of people win, not just an individual.
There is so much that already isolates us from one another. Stories that are about Us instead of Man show humanity in its best light, and inspires it in others.