There are a few use cases where a plugin developer want's to create tasks for users but the tasks can only be completed via another tool / interface.

Some examples:

• If we added assigned JIRA issues to your WorkBox tasks, it wouldn't make sense to "tick" an issue off your list, you'd want to go through the JIRA resolution screens to close the issue off.
• Ad-hoc Workflows use case:

  For Adhoc Workflows Tasks it is only occasionally that we would want to prevent a user from completing a task without being on the page the task is created in. i.e some users use tasks for compliance reasons etc that wouldn't be happy if users can complete without viewing the page. For approvals however most use cases would expect that a user is on the page that requires approval. Hence being able to stop the linked task from being completed from within workbox would allow us to show a user all their items in a single place, but enforce navigating to the page to complete/remove the items from the list.

If you are a plugin developer and you've got other use cases, please comment on this issue and let us know!