Not that I watch CBS News or any other network nightly news, but Bob Schieffer always struck me as a class act. He at least seemed like a professional journalist, and was a welcome antidote to the increasingly bizarre Dan Rather - if Schieffer was willing to keep doing the job, CBS was nuts to let him go. Katie Couric comes across as a frivolous, high-demand ninny, not someone to be taken seriously - network nightly news is a dying journalistic form, and she isn't going to prolong the death throes.
Not only that, but Bob Schieffer appeals to the 80+ year old crowd that watches CBS news.