Whatever the linguistic details, one of the main roles of RSS is to supply directly to you a steady stream of updates from a website. Every new article published on that site is served up in a list that can be interpreted by an RSS reader.
Unfortunately, RSS is no longer how most of us consume "content." (Google famously killed its beloved Google Reader more than a decade ago.) It's now the norm to check social media or the front pages of many different sites to see what's new. But I think RSS still has a place in your life: Especially for those who don't want to miss anything or have algorithms choosing what they read, it remains one of the best ways to navigate the internet. Here's a primer on what RSS can (still!) do for you, and how to get started with it, even in this late era of online existence.
If RSS is so great why aren't people using it? Why isn't there a dozen readers on the market?
maybe it's just not that useful and that's why nobody is using it.
This is a common logical fallacy known as "argumentum ad populum" (appeal to popularity). You equate the popularity of the idea as a basis for determining its validity.
Compare, "if cars are so great, why is everyone still riding horses?"
But everybody isn't riding horses. In order for your analogy to work it would have to like this. "If horses are so great why isn't everybody riding horses to work"