I haven't noticed this, since I don't peruse the glossy rags anymore, but I would think that it is more of an effort to make an item stand out, as a white background makes things look more clearly defined. How many business reports are done on fancy colored paper? Yes, it cost more money, and makes it more difficult to read....not exactly a win/win.
And YES.....you do have too much time on your hands. ;^)
And YES.....you do have too much time on your hands. ;^)