Because the Kid is bullied and largely ignored at school. He comes home frustrated that he so insignificant in his local social structure, so he goes onto the internet where the anonymity gives him the advantage of being able to express himself in a fashion that is not far off "hey guys, check me out, I'm here".
It's sad, but one day he might grow out of it with a little luck. If he doesn't, he'll likely end up as one of these kids that lives with his parents till his 40's and remains a virgin forever. I'm betting on the latter right now, though.