To be successful at promoting ones writing, you must understand a single truth to the human condition; people are lazy. Especially when you haven't paid them extra to make any further effort. If you don't make it as easy as possible to publicize you or to promote your work, you will have less success in dealings with radio, print, television or any media, really.
In my dealings with authors and publicists through my Blog Talk Radio station, KWOD, and in my capacity as the Managing Editor of The WOD Newspaper and NewsZine, a pop culture and fan convention newspaper, I have witnessed a total lack of understanding what a media kit is and what components are needed to be included. Even in my capacity as the host blog site for over a hundred authors, showcasing their works, I have seen the need for an organized media kit. It is undoubtedly, the single most important tool in your arsenal.
The author's success in book sales can be directly attributed to how organized their media kit is and how easy this information is accessible in paper format, as well as digital files for emailing easily. You will give your hosts and event coordinators NO reason to NOT use your materials. The more opportunities a reader has to find out about your book, the more sales you will add up.