You could be right, but so far individual in-game user information could be stored in a small file and in a whole database those users are probably insignificant storage-wise. Let's be honest, they don't have the same amount of users and user-info as, let's say, world of warcraft, which of course is a very exaggerated example to pick with literally millions of users, items and a whole lot of quest-data. A flag to mark an account as inactive after a certain time-span would be more logical and customer-friendly. That same flag would prevent users from showing up in account searches.