Why do they do this half of the time?
Because they are frauds. But not every photo in the media is a fake. And I don’t see the reason to fake this one, or the evidence that it is fake to begin with. There are plenty of real photos available that show the candidates in front of flags if they really needed one.
Look at the original photo in the article (the small one). It is a different photo than the one posted from the Time site. It is taken from a slightly different angle (or Obama had moved) and Richardson and Shrillary and the other woman are looking in different directions than the Time site photo. That one has the flag also. Did this photoshopper photoshop a whole series of pictures and choose the best one? Seems like a stretch to me.