It’s common for a Southwest flight to end and some passengers to stay on the plane. That’s because on ‘through flights’ passengers connecting on the plane’s next segment stay on board while everyone else gets off. Then a flight attendant counts the through passengers on the plane. They can get off to stretch their legs and reboard (with the same boarding pass as their first flight!) or stay where they’re at.
But it’s very unusual to see everyone getting off the plane, and a passenger just decide to stay. They even melt down in a scream when a flight attendant pressures them to leave.