There are a lot of reasons to do things this way. First of all it was originally distributed as a pdf e-book. An ebook even if the same length as a long blog

There are a lot of reasons to do things this way. First of all it was originally distributed as a pdf e-book. An ebook even if the same length as a long blog post makes you more professional, or at least appear to be so. Once you have the pdf, it's trivial to upload it to site a like slideshare and let people view it there. As a side note, because Charlie has worked with Seth Godin and this is something Seth does, he probably is just emulating something that worked for seth. I'm not sure if it says it in the ebook, but this originally was going to be a guest post, but ran a little long.