Pages that are used to redirect to an existing article should be added to this category. This will help with the Affiliated Wikis program as the entire category can be imported to the new wiki.
Periodically, it may be helpful to go through the List of redirects to see which directs are being used. Any unused redirects, especially those created by a Page Move, should be evaluated to see if they are useful to keep. Useful redirects would be common mis-spellings of names.