Here's why: Viewers make quick assessment of performances based on visual cues. There's science behind that statement. Consider a study about passionately playing music, reported by Scientific American.
In a new study, nearly 200 novices had to choose the winners of 10 classical music competitions. Some heard a music clip of the top three performances. Others saw a video with sound. Still others watched a silent video. And the participants were more likely to choose the winner if they watched the silent video, in all 10 of the competitions.
Even when professional musicians were brought in to judge the competitions, they picked the winners more frequently from the silent video. Those competitors who played with passion and moved around won their competitions more often than those who stood still.
Hardly anyone ever just sits still when talking with someone else. So consider moving around more on stage if the scene warrants it. That passionate playing could lead to some big laughs and a memorable show.