For most singers energetic dancing will have a horrible effect on vocals though. I don't think "as live" vocals are about vanity, but about giving the fans the best possible viewing (and listening) experience. It frees them up to dance without having to worry about conserving their breath.
If it comes to it I prefer a seemingly live lip synced performance over what we hear on some encore stages. There's a reason most groups have taken to the casual/comical encore stage concept instead of seizing the chance to belt out the song again. We all know most of our faves are not the vocal sons and daughters of Celine Dion. We don't need the proof.
Spot on comment