I should note that United frequent fliers are automatically entered into the lists for upgrade. There are upgrade capabilities which guarantee an upgrade if availability is there, but the upgrade generally occurs long before the lists. The lists are also available online at united.com - examination of flights departing many hours from now will shown significant numbers of upgrade list people as soon as they check in.
It isn't that all 183 or whatever passengers were DYKWIA - likely most didn't think it would happen.
This story is based on inaccurate assumptions.