Our organization uses Chatter as our internal group chat feature. We noticed that the "chat" feature (where we chat one or more person privately) - is gone. We still have the "message" feature, but the "chat" feature was preferred as those messages aren't tracked. Can you tell me what happened?

Our organization uses Chatter as our internal group chat feature. We noticed that the "chat" feature (where we chat one or more person privately) - is gone. We still have the "message" feature, but the "chat" feature was preferred as those messages aren't tracked. Can you tell me what happened?