In real life we use body language and facial expressions to communicate all the time and we change the tone of our voice to convey feelings and create an emotion. We do this naturally, without any thought.
By changing the pace and tone of how we talk, we change the mood and so can create drama and suspense. At the very least it will be more interesting. Our gestures can convey almost anything, from anger to joy, a wave of the hand or a clenched fist.
We are pretending to magicians after all, so why not act the living daylights out of it. Why not pretend the trick actually matters to you and so it should to the audience.
I play with physical expressions a lot when performing, usually to build up to a ‘rug pull’ gag of some sort, but nethertheless it is there and brings the audience into my world. I’m always trying to create an emotion within the audience, and I’d like to think even if you can’t hear what I’m saying you’d understand the sentiment.
Below is link to a TedTalk which I think highlights how although what we do needn’t have any weight, we can give it quite a lot, just to improve the experience and magic.
Last point - The more hand gestures in a TedTalk, the more views it gets.