ETA: No one is pressuring me to blog; for some reason, no one ever has. So the pressure I resent is not being applied to me -- it's making people I really like miserable.
But the real reason I hate all the pressure to blog besides the fact that so many people don't understand how it works?
Because it's being applied to people who, being writers, often already shoulder enough doubt and fear, and it's being sold as "you're failing your book if you don't." I'm sure that people don't intend to do this, but it's bullying, and it's something that a lot of writers – balancing careers, children, day jobs or schooling in any number of combinations don't need. It's like being told to go out and join the in-crowd or the popular crowd when you're in junior high and you're a geek because then you will be ... more popular. Most of us have outgrown that paradigm – but just in case you want to stay on that side of the fence, there's the reminder that your books need this.
It brings back all kind of awkward, and people don't need that kind of awkward. And if the people offering this advice paid a bit more attention to the dynamics of blogging, I think they'd be less likely to apply this kind of pressure.
It's like telling someone that the sure-fire way to be a bestselling writer is to be a movie star – and then expecting them to go be a movie star; the scale is smaller, but the phenomenon is not appreciably different, imho. Some of us can act. Some of us can't. Most of us will never be movie stars, even if we are all forced to audition. But the auditions, such as they are, and stretching a metaphor to near-breaking, can make the entire process of dealing with the writing insecurities so much worse.
Look, I blog because I enjoy it. I tend to say more or less what I'm thinking about a narrow range of subjects. There are things I won't talk about because I don't feel I own them completely (my kids, for instance). But I enjoy blogging in part because no one is standing over my shoulder metaphorically breathing down my neck and telling me I have to somehow endear myself to people that I don't know and might never meet, with the subtext of failing-your-book wedged in there.