Why certain folders are grayed out in AEM 6.4 under /libs

Here is the details for all new node properties to these similar node

In order to make it safer and easier for customers to understand what areas of /libs are safe to use and overlay the content in /libs has been classified with the following mixins:

• Public (granite:PublicArea) - Defines a node as public so that it can overlaid, inherited (sling:resourceSuperType) or used directly (sling:resourceType). Nodes beneath /libs marked as Public will be safe to upgrade with the addition of a Compatibility Package. In general customers should only leverage nodes marked as Public.
  
• Abstract (granite:AbstractArea) - Defines a node as abstract. Nodes can be overlaid or inherited (sling:resourceSupertype) but must not be used directly (sling:resourceType).
  
• Final (granite:FinalArea) - Defines a node as final. Nodes classified as final cannot be overlaid or inherited. Final nodes can be used directly via sling:resourceType. Subnodes under final node are considered internal by default
  
• Internal (granite:InternalArea) - Defines a node as internal. Nodes classified as internal cannot be overlaid, inherited, or used directly. These nodes are meant only for internal functionality of AEM
  
• No Annotation - Nodes inherit classification based on the tree hierachy. The / root is by default Public. Nodes with a parent classified as Internal or Final are also to be treated as Internal.