CMS or NOT CMS
This video just shows and example of a NOT CMS we built for a client. Sure they can add content and manage it BUT they did not need all the extra features that come with Wordpress or Drupal like workflows, versioning, intricate roles etc.
Also they had a huge need to easily deploy all of this work. For example the Help system can have updates deployed to all of the sites via one Github commit.
So in this case the need for spinning up new instances for clients, easily updating 100s of sites and keeping the whole UI simple far out weighed all the other features Wordpress and Drupal gave you out of the box.