...instead of using the Atom syndication format?
Atom is a well-defined, general-purpose XML syndication format. RSS is fractured into four different versions. All the m
For the same reason that every "better" solution did not succeed for mass market. RSS is widely deployed and it solves the same problem Atom is trying to solve.
Personaly, I have a large number of RSS feeds that I generate myself. They are working today and solving a problem. I wonder how you could convince me to rewrite all those feeds to Atom just to use a "better" format.
Now if you consider how the REST architecture is gaining visibility these days because of better and simpler caching and scalability, these are real arguments. I understand that Atom is closely related to the REST hype and it may be the best way to market it. As REST will be gaining visibility, so are its related formats like Atom.