Use case is we have documents which needs to be restricted based on the user group and can't move those to different folders. We were exploring various options to achieve it. We thought of adding the CUG values via custom metadata schema.But just wanted to check the reason why that is not available OOTB.
We used to have the same feature in classic UI from starting and it was the feature request to add similar changes for touch UI as well.
Assets UI now allows CUG to be set via the Folder Properties within the UI. It is possible to set CUG at the individual asset level however there is no UI for this and would have to be done programmatically or via CRXDE. At asset level, it can be applied by adding "rep:CugMixin" in jcr:mixinTypes and defining principles at rep:cugPolicy node at the asset node.