Scenario:

A large firm has 40,000 users in their LDAP. They are using Crowd to manage these users. They have Confluence, JIRA and Stash connected to Crowd. Only 2,000 of these users have access to Stash, but all 40,000 of them appear in the user management areas of Stash.

Also, if a directory is read only, then these users without access cannot be modified at all.