Talking all day, every day, on the phone is tough on the voice. If you make your living that way, strain on the throat is a threat to your livelihood.
White's Technique is an invaluable help to call centre workers who face that risk. Crucially, it takes the strain off the throat and so helps avoid taking time off from earning your living.
But there's also the positive aspect of its effect on the way you sound. White's Technique can give your voice more authority and more range of expression, making it more pleasing to the listener and hence more persuasive.