They seek to distribute those books through the same channels using the same marketing processes that have served them well in the past. (massimomarinoauthor.com)
During the period of exclusivity, you can not distribute your book digitally anywhere else, including on your website, blogs, etc.. (unrulyguides.com)
There is also the matter of having the ability to distribute books on a wider basis. (ebookreaderguide.com)