Or maybe a better question is why do we need a format different from HTML?
An even better question is why do we need a format different from XHTML?
The 'next' version of RSS should be a syndication module attached to XHTML that calls out the syndication information. Isn't this is what the semantic web is all about? The same information can be viewed either in a web browser or aggregated into a news reader.
Took this picture while on the trip, reminded me of Shelly's ThreadNeedle application.