To echo what Commander Brooks said, not every Retired Account is a player who is no longer with the site. We don't change the names to say who they play now because it looks bad on the forum, and sometimes players need a fresh start without any of the baggage that came with their previous characters - creating space between them can be refreshing/necessary.
As for players who have left, some remain in contact, others do not. When I was a CO (many years ago) I would try and keep in contact with former players where possible, but sometimes former players wish to be left alone. It is a balancing act between trying to be friendly and respecting their privacy, especially if they left for personal reasons that may make life difficult for them. Others, sadly, are no longer with us.
The key is to keep looking to the future; though it's always great when former players return, and we welcome them with open arms, it is new players that are the future of this site!