It's a metaphor to illustrate than someone can suddenly disappear. It can be a bus, a plane crash, a murder, jail time. It happens once a while.
I'd buy a bus with my winnings and put the lottery factor into effect for my former coworkers.
Obligatory: https://en.wikipedia.org/wiki/Hans_Reiser
But yeah, I don't even walk out in front of vehicles that I'm not certain will stop when I have a green light and they have a red light. This surely pisses some drivers off when I stop in the middle of the road waiting for them to stop. They seem to be like "I'm not going to kill you and I'm offended you act like I will".