There's something swaggerific about putting your hands in your (suit) jacket as opposed to your pant pockets. It's a style that definitely separates the men from the boys. I have consciously adopted it as well because I find it comfortable and that it helps me avoid the infamous school boy look, which, to the discerning eye does very little in endearing itself to the viewing audience. One could say it is a style almost synonymous with Italian men, however anyone can execute it. Whether it's one hand or both, swagger you will exude. You will stand out for all the right reasons and for those reasons you ought to give it a try. There's nothing more to say on this issue, however you can browse the rest of these images to see exactly what I mean.
Last three images taken from the Sartorialist.
PG: Man to man, generation to generation.