So often in real life, when a str8 boi finds himself alone with a confident Black King, chances are very high the boi feels some urge to kneel down and serve. The lack of societal/peer pressure allows a white's natural instincts to surface and the Black King's dominant presence will exploit the weakness.
With porn, the total secrecy magnifies that dynamic many times over. Without realizing what's happening, the boi suddenly finds the Black Man has seized ownership of his orgasm, rendering his seed null and void by remote control. It's such a soft, intensely pleasurable k!ll that, by the time the whiteboi senses the danger, resistance is already futile. Might as well make the most of the one-way journey to whiteout.