John Woo has a lot to answer for. Besides affording dove owners a second revenue stream besides fancy weddings and increasing the amount of Christ imagery in action movies to dangerous levels, the hugely influential Hong Kong director is almost single-handedly to blame for shoot-outs where people dual-wield guns. Of course it looks cool. Doing anything with both hands looks cool, from playing the drums to rowing a boat to punching two different people in the face at the same time. Like many action movie cliches this has mainly reached popularity thanks to The Matrix films, which is full of dual-wielding idiots. You look cool, but it makes you a terrible shot. It's pretty obvious why, too, if you think about it for more than five seconds: to aim, you need to look at who you're shooting. Holding a gun in each hand is stupid because you can't aim both of them, so you'd be firing completely randomly.
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/