For those who haven't memorized the schedule, this would be FL 1182 LGA-MSY.

Likely last minute no shows and there was nobody left at the gate so the agent closed the flight and off it went. It's common for a flight to be overbooked and at risk of oversale and then go out with empty seats.

With a delayed departure, that is a strike against having the GA do onboard UG's and delay the aircraft further.