When Did Encores at Concerts All Become the Same?

The band finishes up their last song of the night, and they give a wave to the crowd and walk off the stage. The lights don’t come up, and within a couple of minutes, they’re back to play a couple more obligatory songs before the house lights come on for a final time. This pretty much describes any concert nowadays and any encore. But how did the encore start, and is it anything like it used to be?