Why did Starbucks hire the William Morris Agency?

I'm still scratching my head over the relationship between William Morris and Starbucks. If a proprietor (Starbucks) wanted to find the most interesting projects that were great matches for its stores, why would it enter into a relationship with an organization for whom recommendations would seem to pose such a clear conflict of interest? As a corporate leader, I would personally prefer an unbiased literary partner, not one for whom obvious and inherent biases would seem almost overwhelming. This is no jab at William Morris. I'm neutral about most literary agencies -- they do good things, and they are over-rated at other things, but mostly they're fine, and I recommend that all of my academic authors who move out of the university press publishing realm seek competent representation, preferably from agents who have also worked inside the publishing industry at the highest level. Still, how can any talent agency do such a job without consistently preferring its own properties and projects? Anyone with industry insight is welcomed to comment.

For those who read this occasional blog for its bits of literary industry detail (what few I know, being an 'umble Washingtonian), sales in a store like Starbucks are known as "special sales" (i.e. book sales outside of traditional literary outlets such as bookstores). I suppose the classic special-sale example is a cookbook bundled with a bread machine, so that every sale of the bread machine results in an automatic book sale as well. But there are other cool special sales opportunities, and getting your book picked up by a national coffee chain is certainly one of them. So what happens if you're the author/client of another agency? Do you have a prayer?