I would say it's a combination of a number of reasons, some -- if not all -- relate to the technologies encapsulated in RSS. First, because RSS by design is me

I would say it's a combination of a number of reasons, some -- if not all -- relate to the technologies encapsulated in RSS. First, because RSS by design is meant to just be metadata, and because it's really hard to render HTML (especially those that are not well-formed) the readers typically have to jump through so many hoops to get things just working. Second, I think it's also because the RSS readers are typically developed by non-designers. Although Google Reader keeps it simple, it's utilitarian and mostly not very pleasant to look at. I've tried others (which are also free) but typically it doesn't come close to making it enticing to read. Maybe someday someone will do a feed reader that renders articles in a sane and readable way.