I think the issue is that GAs for whatever reason that is beyond me don't want to make honest and complete announcements. Maybe they just don't want to be bothered. For example they fully know when a departure time is a decision time or that it's a departure time as a "placeholder," But rarely is that information communicated to paxs. Instead paxs think their flight is leaving at 3PM (or whatever time) and no way that's going to happen. A/C swaps do happen and GAs should inform paxs that if you wonder away and don't check back at the gate every 15 minutes or so we are leaving without you if something changes.