Southwest is the airline in the only airline in the free world that makes pilots wait until all pax are off. You see at Southwest when you are done flying for the day you have to wait 20 min sometimes more for the next crew because we have one van to the hotel for the whole crew but we have throughs onboard so the FAs have to wait and thus so do the pilots.

At United the pilots can leave right away. United FA's are allowed to use the aft Emergency Exit light switch if they need it, and check the girt bars.

There is a reason Boeing and Airbus have Emergency exit light switches in the aft galley. It is so the pilots can leave without babysitting the airplane. The United's FOM specifically says to turn off the emergency exit light switch as you exit the aircraft, even with pax.