[[!comment format=mdwn
 username="joey"
 subject="""comment 4"""
 date="2016-03-28T13:22:35Z"
 content="""
For the simple reason that git-annex doesn't know the mime type of a file
before it downloads a copy.

There are some more complicated reasons involving preferred content
expressions needing to evaluate the same way in different repos, which
can be on different computers with different versions of the magic
database, etc.
"""]]