For blogs that are seeking to make money out of advertising, it is difficult to justify why they should send out the content out as RSS feed. If you send full text, then user does not come to the site. If you send excerpts then users are not happy.
One thing to try out could be push full fledged web pages inside the RSS feeds. Instead of just getting the text, I would get images, layout and advertisements as well (but of course still just the content, not the "chrome"). Reading this kind of blog entry on my "RSS" reader would be more like looking at the actual web site of the blog. Consuming large amounts of web sites this way would be faster than visiting them one-by-one with the browser. Publishers benefit could be that users would browse through more of their content (on web I usually pick few articles to read, with this I would probably cursory browse through most of content (and get exposure to the related ads).