Projects typically accumulate a wealth of documents. From workflow documentation, to roadmaps, to shared credentials. All of these need to go somewhere. So, why not put them where your team has to go already, right in Jira. This way users that need them can easily get to them without having to remember yet another url, or manage the separation between project docs and JIRA issues. Simple Wiki allows you to do all of that, without the need to add another server for confluence, or manage another tool somewhere else. As an added bonus, SimpleWiki integrates with JIRA, and thus you can easily mention users, link to Issues, and so forth.