Copyright has benefits for authors as well as publishers.
Moral rights (see Berne 6bis
http://www.wipo.int/treaties/en/text.jsp?file_id=283698) are retained by
authors even after transfer of copyright. These include attribution rights and
the right to object to certain modifications.
Examples
The point is that the dominant role of copyright in scholarly publishing is to
benefit the publisher, to the detriment of OA, not the author. In fact it is
argued that OA benefits the author.
This is why Wallinsky's simple OA proposal is to reduce the copyright term to
the minimum needed to mai