It's actually not the worst option out there. It's better to hold the guns between the legs, so you can aim, but the general position is decent for when there's no cover, and is used in real life. Basically, it allows you to absorb shots with your less-vital legs and ass, rather than your torso although, there's still a very real chance of bleeding to death no matter where you get shot, despite how badasses on TV like to shrug off "flesh wounds" .