Part of being 'cool' is looking like you can do things easily which are generally considered difficult. If you are firing a gun, and you take the time to hold it properly and aim carefully, it shows that you have to really try to hit someone. However, if you can just point your nine offhand at some wack-ass punk even while holding it sideways (and perhaps simultaneously taking a swig from your 40oz.) and still take the bitch out, you must be some kind of badass. So, in that context, it kind of makes sense that it looks cool.