You always have the option of turning off WiFi, not buying from Kobo, and not doing a sync except as part of the update process. Kobo bases its recommendations only on what you do on the Kobo site and the books you buy from them.
Look at the current prices of ereaders like the Touch. Do you really believe that there will be eInk readers with new features and an improved reading experience if the people developing them can't also promote the purchase of books from them?
Kudos to the developers for taking the in your face selling part off of our home screen and for developing a desktop app where one click will remove the necessity of thinking about buying books from them from our field of vision.
Those are not marketing based decisions.