You're looking at it too literally. A grid is meant to be a basic visual system -- a framework in itself really -- that brings order to 2D design and usually gets obscured by graphics. All of these are based on exacting grids: http://www.webdesignerwall.com/trends/best-of-css-design-200... some more apparent than others. Of course, the value of a framework of a framework is another question.
I suspect that is why certain designers are attracted to them. But is also why I click away wondering "why would anyone ever do that?"