DIME Use Case?

I've read the DIME I-D and the mailing list archives, but it's still
not completely clear to me what the use case for DIME is indented to
be. Can someone either explain or point me to the relevant document?

The immediate question that comes to mind is:
DIME seems to cover a lot of the same territory as MIME. Therefore I
presume the idea is that there's some application for which you
believe MIME is inappropriate and you expect to use DIME instead. What
is that application?

-Ekr