It puts zero emphasis on connection.
Yes, sex is about pleasure. It's about getting off, and fulfilling needs, and releasing and blah, blah, blah. But it's also about connecting with another individual.
Porn portrays a woman's body as a mean to an end, and it's a dangerous idea to entertain. The woman underneath you is a person, maybe someone you care about. And part of the genuine, real deal excitement of sex is getting close to that person in a very intimate, personal way.
It's easy to forget this essential aspect of sex when you watch women on-screen moving their bodies just for someone else's pleasure (yours), and nothing more. There's more to sex than just two bodies slapping together. It doesn't always have to be love, but a routine of it being strictly mechanical can't be a good thing.