When using volumes, the usefullness of the volume is limited without coupling it with a data-container.
The reason for this is the tie between a container and the volume... when the container goes away so does the possibility of actually using the data in that volume again, unless you'd happened to copy the host path of that volume.

Sumary: referencing a volume is impossible when last container is removed

Proposed Solution: Provide volume management API/UI. This has started to be implemented in #8484