Python - Why use anything other than uuid4() for unique strings?
Using a hash to uniquely identify a resource allows you to generate a 'unique' reference from the object. For instance, Git uses SHA hashing to make a unique hash that represents the exact changeset of a single a commit. Since hashing is deterministic, you'll get the same hash for the same file every time.
Two people across the world could make the same change to the same repo independently, and Git would know they made the same change. UUID v1, v2, and v4 can't support that since they have no relation to the file or the file's contents.