because porn viewers have been conditioned to "porn sex" and that has become a fantasy itself, its so un-realistic it serves the eye more than the brain. its typical characteristics are:
* un-real repetitive sounds
* as little as possible physical contact to allow better camera shots that show more of the bodies
* external cum-shots to "show/prove" the viewer that the actor actually came
* ridiculous facials where the receiver typically winches in disgust while getting cum on his cheek. or even worse with str8 porn where the female does cum-bubbles with saliva.
* typically limp cocked bottoms that shout like they are in extacy
* typically the most un-confortable and ridiculous sexual positions to showcase variety.
this has created a porn-sex school which a) actually differentiates porn and real sex, and B) makes porn sex "larger than life" so people cannot replicate it and as such is more valuable.
So basically Armond Rizzo / Joey Rodriguez with duct tape over his mouth ?