I understand the upsides of OAuth and initially we attempted to use OAuth in more apps, however more users prefered using ldap for tighter integration, as ldap usually gives a better user experience inside the app not leaving the app first for the redirect. Also the auto login mechanism in OAuth was sometimes confusing. We won't put up the effort at the moment to support multiple auth backends directly in the app installation/configuration out of the box as that increases the testing amount to ensure proper updates.