The best rescue is the one that never happens.
Rescue class, done well, tends to be an eye-opener for many people. It points out a lot of the subtleties that are usually missed, and by drawing your attention to the precursors of incidents and accidents, it affords you the opportunity to recognize them and break the chain of events.
Knowing how to do CPR, or how to treat a diver going into shock, or what to do in such-and-such emergency is something that can save lives when those emergencies come up. That is how your taking rescue may help others. Gathering skills to prevent bad things from happening to you (or to handle them when they do) is what will help *you*.
I took rescue with a friend with whom I often dive, and since we took rescue we both have become much more adept at calling dives. I suppose that means we haven't made as many dives as we would have had we not taken rescue and learned how to be cautious, but perhaps by learning (and being given "permission" by that learning) to know when to say when, we may have avoided a snowballing incident.