On a private flight, you either own the aircraft or have booked the whole airplane for the entire trip. Now you control the schedule, where you want to fly from/to and when you want to leave. Most private flights depart from and arrive at regional airports and all of these are less congested and often much more convenient than International airports.
Here, there are no check-in queues, no complicated security or immigration and no slot delays for take off or landing. You drive straight to your waiting aircraft, get on board and can literally be in the air within minutes.
Welcome to the world of private aviation.