Why would I need a first aid kit when I have 911 and NGV ? Neither of two great things will prevent the injury , they only stop the bleeding after the fact . Here’s a simple , logical example even you can follow .. if you are coming at me with the intent of doing harm and I pull out my brand new , white box that says first aid on it , besides smiling at me  , it’s not going to change your mind . Now same scenario, switch that first aid box with a 9mm and visual red dot laser that you see coming out of the end just below that hole , and resting dead center of your chest . You will stop smiling and start thinking .