Duplicate Packages from Debian archive in DMO

Hi,
This has been a question that's been asked in the debian-devel mailing
list and among the Debian multimedia team recently. Why are packages
already in the Debian archive still being uploaded to DMO?

For example, there is lame, x264, and xvidcore which have been
uploaded to the Debian archive, migrated to testing, and backported to
the stable release. Yet I see that at least lame and x264 are still
being updated in DMO. Is there any particular reason why?

--
~ Andres