Personally, I did not see much point in this, you can use it to fill the structure and attributes, you can see and filter them, but you can not use it without the item.
They can also be linked to the item using the ics_connect utility. Empty ICOs are also used when working with part family, for which you can then generate 3D
By stand alone, you mean ICO not connected to any business object (item/rev)?
Can be utilized when using MRL and Vendor Catalogs for example. You can import the tool ICOs (in tens of thousands) without the actual tools (items), then generate the tool on demand.