Why aren't new revisions being created?
Revisions may not be created if only the layout canvas is edited on a node. A patch to the entity reference revisions module is required.
When editing a node if only the layout canvas is edited, a new revision won't be created unless you have applied this patch to Entity Reference Revisions module. More information about this issue can be found on the Drupal.org issue queue.
This patch is included within the DX8 composer.json and is installed if patching is enabled according to this post on Github.
