I think you use confluence because it integrates with jira, and you use jira because it integrates with bitbucket and your software lifecycle / change control management processes, and you have those because you've got compliance requirements and the tooling needs to be managed by people who don't want to get deeply invested in some complex DSL when a visual workflow builder's "good enough"

See also "nobody uses elasticsearch because they like lucene queries; they use it because everyone likes using kibana and tolerate lucene."

(There are probably people who specifically like features of confluence or elasticsearch; most use it because they like / must use other parts of the ecosystem and feature/product N is good enough)

[edited to finish the thought about jira's workflow management]