Pokemaster doesn't delete accounts unless they are truly unnecessary, for example, Trolling accounts.
If he were to delete accounts, information would be lost, and it would just remain a big empty, wasteland, and honestly, it would bring up a lot of confusion.
While this would (most likely) never happen, we could, for instance, have a section of users that have been inactive for _____ months. This would be more useful and would defiantly help sift through inactive users, but I do believe that the current system is fully functional enough as it is right now.
Not to mention, I was myself a time inactive, and (believe it or not), asked for my account to be deleted. But, if Pokemaster followed my wishes, I would not be here today.
And I love being here, so just because someone is gone for a while doesn't mean they won't come back.
Anyways, I think that covers it all. You can comment with any other confusions, but I'm afraid this just won't happen.