Not always PAX fault
Well, it is not always the PAX fault. In the "we will call you when the flight is boarding" Swissair lounge at LHR a few years back, they did not call us. The flight had never gone to "boarding" (= inbound aircraft has arrived) let alone "last call" (= aircraft will start boarding at about the time it will take to walk out from the lounge) on their screen. "Oops" was the answer. When a colleague and I got to the gate, the flight had been pushed back... SR took responsibility and gave us hotel vouchers. Then called us as the aircraft had gone technical and returned to gate. Left an hour or so later.
Still a mystery how people can check bags then miss the flight first thing in the morning. Perhaps they have checked in bags the previous day, then don't make it to the airport on the morning itself, for whatever reason. Getting sloshed seems unlikely at that time.
Momo