The network effect of Jira is obviously at the department level; dept. head A mandates Jira. User B gets moved to new dept. C, we need some sort of project management tool - hey B what did you use when you were working for A, oh A likes using Jira, I didn't like it much but it's ok I guess.
Ok folks, let's use Jira!
Dept. Head A moves to Dept. D, hey everyone we are going to start using Jira.
Dept D. is being merged with Dept. E, Dept and new Dept. Head J is joining. E is using some open source Kanban solution based on CouchDB, hmm, let's go to Jira - other departments are also using it and then we can get rid of the CouchDB thing!
In point of fact where network effects of Jira is concerned, I have put some effort into learning JQL and setting up my own dashboards, so when you give me one of the competitors I get grouchy. I prefer Jira or Trello - also owned by Atlassian iirc?