Most authors believe in the value of book promotion. Not all authors can invest their time and resources in robust book promotion campaigns, but nearly every author I've run into over the years wishes he or she could do some book promotion. It's simply very unsual for an author to care enough to write a book, and publish a book, but to not care enough to back it with a book promotion campaign.
The only exception to the rule would seem to be professional book authors and academic book authors. Their target audiences can be so specific that it would be difficult to reach them through the usual channels. Book promotion campaigns that revolve around the mass media just don't always work for these very specifically aimed books.
But even authors of professional books and academic books need to do more than publish their work and hope their intended readers find it. They need to proactively make sure their intended readers find it.
Some sort of book promotion campaign is in order. Even if those book promotion efforts don't include pitching national television shows, book review editors, and so forth, those book promotion strategies might well include writing articles for niche publications, maintaining a blog, and -- of course -- creating a book Web site that's rich with information and resources.
Book promotion campaigns do make sense for professional and academic books. Those book promotion campaigns might take a different form than book promotion campaigns for trade books, but make no mistake about it. If you want to get the word out about your book, you have to actively take all the right steps to make it happen. That's what book promotion is all about.