A good blog exists independently of people reading it.
Even if no one read my blog, I'd still write it. Not exactly sure why. Maybe it's something like this -- I would still cook even if I was the only person eating.
I write because I am a writer. It would be the same if I was being paid for writing vs doing it for free, which is pretty much how I've always blogged. There was a brief time when pieces I wrote here were edited and published by Wired. But I still wrote the same stuff.
Some people seem to feel the need to justify blogging, blogging is still alive they say, but it's actually more than alive blogging is a cultural fixture. Thriving. Read this piece in today's NYT about two Japanese hostages in Syria. They both kept blogs, and their writing informed the reporter. This is why we don't need interviews so much these days. If you have something to say you should be blogging it. (And the hostages weren't available for interviews, in fact one is dead.)
Recently I've been writing stuff on Facebook, because the engagement level there is so high. But I've found that if you want people who don't use Facebook to read you, and there are important people who don't, you have to put it somewhere else, and for me that's here on my blog.