Encore?

Why do artists cut their concerts short only to have them come back after the audience claps and screams their heads off? I mean what's the point of it? Last night at the ACC we watched as John Mayer and his band stepped off the stage. The crowd was cheering (screaming) for more, people were clapping and waiting in anticipation for him to come back. I didn't make a peep. Of course he was coming back -- he hadn't sung fan-favorite songs like "Daughters" or even "Body is a Wonderland" yet, so there was no way he wasn't coming back for an encore.

Of course in the end I was right, he came back to sing one of my favorites "Stop This Train", followed by at least 3-4 more songs. You just kind of knew that he was coming back.

But seriously, why do artists do this? Is it simply for a break to get some water/alcohol, and maybe to take a short nap? Maybe they went back to the check scores? Why not perform all your good songs and then just leave it at that?

If he had just sung Daughters, I bet I wouldn't be half-deaf right now.