Immature people who aren't educated on sex can use porn as an indicator about how sex really is. Immature people who aren't educated on relationship can use Twilight as an indicator about how dating really is, too =p It's a two-sided coin. It's not porn's fault, it's just stupid people.
I know people in relationships watch porn, but we can't forget that people in this current generation aren't getting into relationships until they get older and older. A couple generations ago, by the time you turn 18, you moved out, got a job, and very soon after got married. Currently you turn 18, go to college, probably move back in with your parents (How's YOUR economy doin'?), MAYBE get a job if you're lucky, and MAYBE move out. It's practically normal now for people in their early 20s to still be living with their parents because of this "everybody is supposed to go to college" thing.
What does that have to do with porn? People getting into relationships later and later, getting married later and later, so young men would obviously be watching a lot of porn, and not getting any relationship experience until later in life than those in earlier generations. I'm 18 and I've never had a boyfriend, so, y'know. -Shrug-