Television exists to sell products. In addition to hawking laundry detergent and SUVs, television sells books. Lately, a few titles have rated full-fledged commercials, but usually television sells books through interviews with authors on talk shows.
This is a win-win system for everyone. Talk shows need guests; audiences benefit from learning about new books; and authors need free publicity. So when Dan Rather turns all 60 minutes of the venerable news show 60 Minutes into an infomercial for Bill Clinton's new book, My Life, and when the Today show mends its feud with Good Morning America to simulcast an interview with Mr. Clinton, and when all of the news shows and 24-hour news networks cover Mr. Clinton's appearances on all these other shows, they are selling a lot of books.
The eagerness of broadcasters to turn themselves into Home Shopping Networks to sell Mr. Clinton's book illustrates the media bias in favor of this particular former president. (Why didn't Richard Nixon get on all the interview shows? Or Jimmy Carter?) It also shows the limitations of the visual media in dealing with the written word.
Television likes larger-than-life personalities with charisma and a hint of scandal, so Bill Clinton is its perfect celebrity-author. Other authors that were big on television were Gore Vidal, George Plimpton, and Truman Capote.
But most authors are not "personalities"; they are writers, and coming to terms with the printed page is very difficult for a visual medium. Oprah actually did a good job at this with her book club, since she hosted the authors only after she took her legions of viewers through the process of reading the book and discussing it.
C-span also does a good job with books, typically having a host sit down with an author at a table to talk not about the author but about the book. To be sure, this is not very visual; it lacks television pizzazz. But written words need to be treated by words, whether written or spoken. The visual medium, with its sensationalism and celebrity-mongering, just gets in the way.