I agree with this, of course. But en: treats unfree content as deserving of many of the same protections from deletion as free content, and deleting a "fair use" image that we're not actually using will provoke people into accusations of ignoring process, abuse of admin tools, and may even wind up at Deletion Review.
It it process. It's CSD I5. You tag it, wait 7 days, and then delete it. Not a very speedy form of speedy deletion, but it's on the list.
I'm not sure why we give people so long - they can upload the image again if they find a use for it. I would suggest reducing it to 24 hours (enough to account for images being removed from articles without consensus, any longer is unnecessary), but I'm not really involved in the image side of things, so I'll leave it to someone else.