Flight delays and arranging back up protection

Why is it that the airlines can never "show" that a passenger has been protected on their next leg of their journey. I've always been under the impression, that the ticket agents, simply zero out a flight in order to use up whatever last minute seats they have. I wonder if this really happens or if it's wishful thinking on my part. Today, I received two calls from passengers with extreme delays on their flights. Go figure, Washington Dulles on United to Tampa (what we really think is the plane wasn't full, so it's easy to blame "mechanical"). And from all places, Heidi and Mark were on a flight from LaCrosse, WI (they of course, don't know why they are still setting on the tarmac, 3 hours after the scheduled flight departure time. Lovely of the airlines to "communicate" with their passengers. I never understood why it's so top secret. *nodding my head in disgust*