Besides it actually being easier for the author to just post the content they're about to read from, and thereby gain valuable hours of their life not having to audio edit and re-record the bodged bits, here's a bunch of other reasons.
Most people, especially me, read much faster than they hear.
If the topic's interesting the author can embed links or I can copy & paste into a search engine for more info.
If it's really interesting and I want to send it somebody I can copy & paste & edit a few snippets and not waste their time with the part they don't care about.
If I myself feel strongly about something and wish to, oh, let's say respond on a BBS forum about it, I can, again, copy & paste the part I'm responding to for easy context to the forum reader.
This "use multi-media for optimum SEO" crap needs to die in a fire!