Per iOS standard design, only one ViewController is supposed to manage a full screen (iPhone) or region of a screen (iPad eg. split view controller). That's because you want to keep the view hierarchy pretty straightforward, instead of taking the view portions of other view controllers and inserting them as subviews of another VC. (Makes you feel dirty). Suggest watching the WWDC 2011 video on Customer Container VC's for an explanation.

Also it would be quite a bit of overkill and extra communication and code to back every table with a full blown view controller.

Ah, and after re-reading your question. Yes this was a design decision, but I've had to use this same bit within a detail controller inside a split view when I've had more than one table view.

The reasoning here was that search results aren't going to come up that often, so we wanted the results out of the way most of the time to make a cleaner interface.