Why doesn't congress blog?

To keep up on the blogs vs. twitter debate, Ezra Klein again lays the hammer down, asking why congress is in love with twitter but doesn't blog:

But this is the problem with the public sphere's quick embrace of Twitter. It's intimacy without communication. McCaskill doesn't actually say anything in 140 characters or less. The illusion of transparency comes because in everyday life, we only hear about the dinner plans of people we actually have a relationship with. What's useful about intimacy, however, isn't the exchange of trivia but the access to different perspectives. And I'd really like to hear her perspective! It would be rather nice if senators and congressmen routinely wrote posts explaining their thinking on major issues. A public service, even. Instead, they've all embraced Twitter.

I started thinking of this when I read John McCain's twitter page and was interested how he never really has to explain anything, it is just political sound bites and trivial goings on. Which is fine, so long as they take the time to ever say anything. Otherwise it is just noise.