We can create revisions, so of course we want to be able to delete them as well.
We'll usually want to delete revisions whenever the revision is no longer pertinent. We would probably always leave the N-1 version of our fileset, but if we have older revisions, we would certainly want to clean up to save on disk space.
If we go into the "Manage Revisions" view, we can select a revision and hit the minus sign to remove it. If no associations exist for that revision, we'll simply get a prompt to confirm:
But, if there is an association, we can choose to remove the association outright, or switch it to another revision: