Legal considerations aside, have you ever tried to publish a book? Do you know how much work would be ahead of whatever person tried to do this? Do you understand the difficulties of designing it, choosing the materials, doing the layout and artwork and design in a way that looks good while making sure to avoid copyrighted images, then finding a good printing company, marketing and advertising it, setting up a store to sell it, dealing with production and shipping hassles, etc?
And then AFTER all of that is done, because of the Creative Commons License the person still wouldn't have the legal rights to their own material, and they might have to deal with people trying to sue them for including their work without their permission(even though such people wouldn't win, it'd still be a big hassle)…and then after ALL that, they would be expected to give a portion of their profits to the site and community?
This is why it wouldn't happen, far more than the question of whether or not they could legally do it in the first place. Such a person would be lucky to even break even on covering what it cost them to get the book produced, let alone making profits and sharing with the site.