...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 major feed readers have supported Atom for as long as I can remember, so why isn't its use more prevalent?
Worst of all are sites that provide feeds in both formats - what's the point?!
There are a lot of RSS feed readers out there that people are used to using, and most importantly, RSS is very well known and has been around much longer. Why mess with something if it works?
Because the developers of sed sights got reemed from their marketing manager that they were "excluding" people by not providing rss. Since Mr. Marketing has never heard of Atom, you just provide both.
If you are restfully implementing it, its not a big deal to just do both and not get yelled at by other departments.
The same reason that people are HTML 4 loose, strict, XHTML transitional, XHTML strict, etc. Legacy code / working with what you already know.
Besides, both formats have their merits. Better to support a couple different formats than have one be-all-end-all-subscribe-to-everything feed that becomes bloated.
Because for the majority of purposes either will work, and RSS has the advantage of being the acronym that defines the category.
Beyond that you would have to email individual sites and ask them.
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.
Vincent, I'm not suggesting that anyone rewrite existing RSS feeds just for the sake of it, that would be a big waste of time! In terms of RSS being the acronym that defines the category, I'm guessing that most users now identify with the orange feed icon, rather than the specific flavour of XML behind it.
The fundamental thing that the Atom creators didn't understand (and that the Atom supporters still don't understand), is that Atom isn't somehow separate from RSS. There's this idea that RSS fractured, and that somehow Atom fixes that problem. But it doesn't. Atom is just another RSS splinter. A new name doesn't change the fact that it's just one more standard competing to do the same job, a job for which any of the competing standards are sufficient.
No one outside a fairly small group of people care at all which standard is used. They just want it to work. Atom, RSS 2.0, RSS 1.0, RSS 401(k), whatever. As long as it works, the users are happy. The RSS "brand" very much defines the entire feed category, though, so on the rare occasion that someone does know enough to choose, they will tend to choose RSS, because it's got "the name." They will also tend to choose RSS 2.0, because it's got the bigger number.
RSS, and especially RSS 2.0, are very much entrenched in the feed "industry." Atom hasn't taken off because it doesn't bring much except a new name. Why switch away from RSS when it works just fine? And why even bother using Atom on new projects if RSS is sufficient? Switching to a new feed format mostly means extra time spent learning the new format.
If nothing else Apple's exclusive use of RSS 2.0 for podcasts means that RSS 2.0 is here for the foreseeable future.
If you are asking why the Atom syndication format is not more widely adopted than the various versions of the RSS format, I think it would be difficult to come to an objective answer. A variety of factors like the amount of investment in RSS prior to Atom, the relative ease in implementing RSS versus Atom, and 'marketing' all come into play.
I can, however, think of a few things that should be considered when choosing what syndication format to use in representing resources:
Atom
RSS
I think it is important to remember that to the end-user, what syndication format you choose to use is not very important, as most feed readers and browsers handle either format equally well. The choice of syndication format however can be very important to the developer, as there are technical details that can impact the software development side of things.
The 'why' was fairly well answered, but I would suggest going forward that developers only implement Atom on sites. There's no reason to have multiple formats for a site available and any modern feed client can now parse Atom feeds.
Atom has quite a few technical advantages over RSS and is being widely supported and utilized by major companies such as Google and Microsoft.
As for branding, I don't really care what acronym is used. I think the universal orange broadcast icon or the word "feed" is what people care about. Despite the proliferation of RSS and Atom feeds, I'd say the average web user still has no idea what they are. Looking at it in that way, the whole concept of syndication feeds is still in its infancy.
I think RSS has a better marketable name :-) RSS is something easy to say, serious-sounding, and virtually senseless. Really sounds like a silver-bullet technology. "Atom" word has sense, but hardly there are a lot of people associating this with some cosmic hi-tech, more usual associations are students, high-school physics, communists' weaponsm hypeware "web 2.0". A very small qty of people out there really corellate it with what it really is and why has it got it's name - an atomic-precise descriptive structured knowledge representation framework. If I say "RSS" in non-IT-pro crowd I've got a very good chance to be instantly understood what I mean today, but if I say "Atom" - hardly anyone will get it any of that fast and clear. RSS is de-facto a name for syndication feeds. That's why think it can be a good idea to label it RSS while technically giving 100% Atom and only Atom - software does not care oat's drawn on a button and end-users will get what they've meant to get. IMHO.
RSS is more simple, that's where its strength is. Atom is better defined, yes, but that's the problem: they made it easy to write a very complex feed when at the end of the day you want a simplified summary.
Why do so many people prefer RSS ? It's easy and gets the job done. You can edit it by hand; not so easy with Atom. Have you ever tried to write a feed reader ?
IMHO, the only thing Atom did good was multiple enclosures.
Why do some websites offer two feeds, RSS and Atom ? Because they can and because some ancient feed reader may not support Atom.