I'd really like to know. Because there are an awful lot of us at it, and we probably all have different reasons.
I blog because:
I am writing, but don't having to worry about whether anyone likes what I've written ( although of course it's nice if they do)
I can tell myself it's work. After all, I'm a writer, and I'm writing, so that's work, right?
I am getting away from the WIP, which like all my WIPs is much better in my head than when it lands on paper. Something seems to go wrong in transit.
(Currently) my terrible injuries make concentration difficult
(Currently again) I'm awaiting my agent's verdict on the first part of the aforementioned (I love that word) WIP, and there's no point in my carrying on until I get her verdict.
I enjoy reading other people's blogs, and like to join in as well.
I am a terrible procrastinator, and blogging is a writing procrastinator's best friend (well, wine and chocolate are good, too).
Looking at this pathetic list of reaons, I feel rather ashamed. There doesn't seem to be a single good one among them. Oh dear.
Please tell me why you blog. It just might help.