Because he’s showing off instead of serving the visuals.

The awkward position, exaggerated movements (that don’t serve his coperformer), and strange angle all combine to make the scene look more like a demonstration of how not to have sex than an engaging and arousing sex act.

Plus, it changes the visibility of the female performer. Which isn’t going to be a problem for everyone, there’s people that watch hetero porn for the male performers, and that’s great. But it does detract from the hetero viewing experience as well as making the scene itself ineffective (or less effective) as porn.