Some have quit diving.
Some are out there diving.
Some have lost the luster on the new penny and no longer follow as closely.
Some have grown tired of answering the same questions for every new diver that comes along and then arguing the semantics about those things with "old timers" who will never get it because they dont want to get it.
Some people tend to get marooned on the island of mis-information like "it's not DIR unless it's black." They couldn't be found if you sent the entire US Coast Guard to look for them and a lot of people no longer see the point in doing a SAR for them anymore.
As cynical as it sounds, that was artfully framed.