No, there has not been a decline in the stand by status of flights. It is still very common practice, especially among airline employees and retirees. The problem with most stand by flights now is that airlines are consistently overbooking their flights as it is in the hopes that they can still achieve a full load after accounting for no shows. Plus, as more and more airlines face financial difficulties, less popular flights are being cancelled or re-routed, leaving less available flights for those that want to stand by. Your best chance for stand by is to choose less popular flights at less popular times, not be tied to any time frame for arrival at your destination and look at multiple city stops on your way to your desired location. Arrive early (first come, first called) and be prepared to wait.