Media Manipulation: the "Bullshot" phenomenon

Target renders. Bullshots. Pre-renders. Grading. Post-processing. A whole new terminology has built up within the games community to describe the ways and means by which game-makers are creating promotional material that may or may not actually look like the product they'll eventually be playing on their consoles and computers. Where did it begin, why are they doing it, and in the internet age where any kind of fakery and shenanigans is swiftly jumped upon, shouldn't they really be stopping it?