We fly under an incredibly wide range of conditions. Our crew composition changes with every outing, and often with every launch on any given outing. We fly on a highly irregular basis. Distractions are legion. Nevertheless, if it can be accomplished, a well established habit pattern may help warn the pilot that something has just been missed.
Interlocks are physical devices designed to prevent mistakes of commission.
Some have suggested that we should hook the harness into the glider before getting into the harness, as a way of making it more difficult to launch unhooked. This makes a great deal of sense, really. Currently accepted practice has us building our wing and then walking around for an hour wearing our cockpits. We finish building the aircraft just prior to launching. Sounds kinda dumb when you put it that way.