Haha you've clearly never worked for a cheap corporate flight department. Now there's the simulation immersion..
"Part 135 setting - On"
*Phone Rings* "Hi, this is Jenny with Hot Start Flight Support, I know you said you were scheduled to depart in an hour but uh,.. your passengers are in the lobby." "Jenny, stall for me! I need the fuel truck ASAP!" *Phone rings again* "This is lead passenger ______. We are ready to go, where are you!? My broker is going to hear about this!" *Phone Rings* "Hi, this is ____ from (broker), my clients inform me that you're not ready for them? What is going on?!"
"Part 91 setting - On" would be your Owner telling you to be ready at 9am and then not showing up until 9pm.