[Engine-devel] 'deactivate' disk - what's the use case?

I'm wondering what's the usefulness of having dual action of attach + activate to get a disk properly attached and working in a VM (and the deactivate and detach counterparts). The only reason I can think of is that we've annoyed the user by this useless dual action when working with storage domains in a data center for ages, and we wish to remain consistent and annoy the user in the disks scenario as well, but there may be a reason I'm not aware of. TIA, Y.