Need 'access civicrm' permission to see system messages

Using a profile to sign up people to a mailing list - they fill in name, email and country and get automatically added to a group. I realised that anon users weren't able to see the messages e.g. 'Thank you. Your information has been saved' or 'You are already subscribed in X. Your subscription is pending' until I turned on the Drupal permission - 'access CiviCRM' for anon users. Doesn't seem that they should need this permission to see these messages, though I may be wrong..