There needs to be a means for Server Admins to delete/clean up subscriptions and users from the system.
Ref: https://help.alteryx.com/server/11.0/admin/index.htm#Administration/Users.htm%3FTocPath%3DAdminister..., “To revoke a user's access to Gallery, deactivate their user account. You cannot delete a Gallery user's account.”
While testing with version 11.0, default permissions set to NO ACCESS, Security using Windows Active Directory, I gave the gallery URL to a random teammate to see what they could access. While permissions prevented the individual from most activities, the server still created a USER and SUBSCRIPTION for the individual. Once testing was completed, there was no means possible to clean up these entries., or at least to do more than set them to NO ACCESS.
For most enterprise applications, it is common practice to be able to purge a user account from a system if they are no longer a member of the company.