Site skins don't have the journal navbar because it would a) complicate the code for the site skins considerably, which would have a small but noticeable effect on page load times and server load, b) require massive visual tweaking to not be a usability nightmare due to having multiple navigational elements; c) have a lot of problems with assistive technology, since many of the semantic labeling we use in both the site skin navigational elements and the journal navbar navigational elements should be unique per page.