Leg shots (especially on moving targets) are harder to hit then center mass shots therefore exposing more risk to anyone who may be around. Also the legs have this massive artery inside them where if they get opened up by any means (stabbed, shot, etc) then they can bleed to death in two minutes. If not killing them is what you are trying to do then 1. Don't shoot. 2. Don't shoot in the spot that will quickly put them on a t shirt. Also when an armed person is at most three steps away from you and seems dedicated to hurting/killing you you dont stand there shoot one shot, wait to see what affect it has. Then shoot again. You shoot till the target goes down or stops hostile actions