You live at home with your parents and you want to go smoke by yourself, or much preferably, with a friend. "I'm going to go drive around," you tell your parents, and it really is true. They just don't know you are going to hot-box the ride.
Any situation where smoking the herb must be done discreetly (as in most situations) so no other parties know. As long as you don't smell of it, hopefully; in most observed cases.