It kinda makes me disappointed when people leave and they state reasons like "doing something more productive" or "moving to another game."
First off, if you want to do something more productive, getting rid of everything that entertains you isn't going to solve the issue. It's just going to make you extremely bored.
Having access to those things, such as television or the internet, and making a choice to do something else more productive is still a pretty valid option. Second, moving on to another game means you are still probably going to be browsing the internet. So it's highly likely he will pass by here and lurk from time to time. If not, come back with an alternative account.
Another excuse that some guy left recently (forgot his name) was for "college." College isn't a big deal at all, it actually gives you a lot more time than high school. I'm in college, and still play games and browse the internet. You set up your own hours, and starting college isn't going to be a big hassle on you unless you take a ton of classes starting out. Which makes no sense. These people that leave for these stuffty reasons really don't have self control if they find it that big of a deal. Most likely they will come back and realize that they still have a ton of free time on their hands.