Ending the show brings things back in focus, prompting everybody to hoot and holler for more. It's a reflex. The fake encore works because it makes the audience think they're getting more than they actually are, like when potato chip makers come up with a new super-duper big bag and fill half of it with air. What the band does backstage before the perpetration of the fake encore varies on the group. I heard Def Leppard used to take the time to fornicate with horny, topless mother-daughter duos.
Most bands probably take a leak or call the limo driver.
The fake encore is an institution, a ruse so effective most of the ticket-buying masses would feel cheated without it. At the very least, it allows savvy concertgoers to leave early and beat traffic. This is Steven Hyden's first piece for Ironminds.