There are distinct attitudes towards blogging - those that embrace it and are already doing it, in their various ways - political commentaries in a journalistic style; displaying art work or fashion interests; sailing or motorcycle travelogues. And those that really don't get it. Some people can't the time for that sort of thing and are not interested in writing about themselves in a public forum. Many people do not have the technical knowledge, or more likely the interest, in blogging.
Blogging is an attitude towards Internet communication, it opens topics to public levels. Blogs are distinct from private emails and social media status updates. There is the difference. Facebook, Google+ and other mass social sites are designed to suck up trivia from people's daily experience to perpetuate a miasma of egotism and Blogging is a writing genre which can bore and intimidate those who are content with Facebook.
As an opposite view I include a poster by Australia Post beautifully promoting the letter as a valid medium for communication. (Image copyright Australia Post)