Why is it "so important?" In the grand picture, it probably isn't. But it IS enjoyable for many many men and alot of women, too. Men on the average truly enjoy "visual" sexual stimulation, and it's now easily and readily available online. He likes it for the same reason he probably likes to have sex with the lights on, for the visual stimulation.
It's very possible your guy just doesn't quite understand your interest in watching internet porn and playing webcam games WITH him because so many women are so vocal against their man even viewing porn at all. It is a subject of so much controversy and often generates so much insecurity in females that it's easy to see a man being afraid to even discuss it with them.
Here's a suggestion, when you're feeling sexy, why don't YOU sit down at the computer and pull up some porn that turns you on, and let him find you enjoying it. I bet he'll be pleasantly surprised and might just sit down with you and join in. Him seeing you actually enjoying something that many many women would shame him for could represent a big step forward in your sex lives. I bet he'd be thrilled to try some of the things you two see together online once he realizes you aren't going to throw a fit for him viewing porn.
He's probably just nervous about his like of porn and does it by himself to stay out of trouble with you. Communication is everything here, dear.
Lisa