It may sound egotistic, but it's also a solid way to build something akin to a 'book' albeit in a discrete blogged form: you tend to quote yourself not to make the same point over and over again in so many different phrasings. It makes the arguments consistent, and rewards thoroughness, paying attention to each post (coherency, wording, etc.) Eventually it builds up a coherent, cohesive corpus of ideas that hopefully, should the theme be well-defined, is a book.
Usually when going for publication, you'd replace these quotes with references to previous chapters, typically in footnotes.
Usually when going for publication, you'd replace these quotes with references to previous chapters, typically in footnotes.