I think we do. There are a couple of templates that still reference Workbook objects, namely
* `/cms/rules/_form.html.slim:19`
* `/cms/chapters/index.html.slim:18`
* `/cms/chapters/_form.html.slim:22`

Having no Workbook breaks the chapters index page (log in as admin, go to Profile > Chapters), so this was purely to make the template more functional after the initial seed.