In my experience, if something happened, its basically the ride system making sure you know it happened so you can respond to it. For example if there's low air pressure, the ride system may have a pilot light go off, and when that happens there may be a set time you have to hit the Acknowledge button before the ride system rolls into say a E-Stop. Now that's a completely theoretical situation that may never exist, but those are the type of situations I believe they're used for.