[Zope] Why would you manually add to a Vocabulary

In the No Starch Book_of_Zope, they walk through the API for manually adding a word to a vocabulary. Why would you want to do this? I don't understand what advantage you would get here. Slightly addled, -- Joel BURTON | joel@joelburton.com | joelburton.com | aim: wjoelburton Independent Knowledge Management Consultant