Everything you own represent a piece of your life where you worked for the wealth to buy it. When a thief steals something from you he's stealing a part of your life. Now am I going to kill someone over a few hours? Of course not, a few days nope, but when it gets into the months necessary to buy a car then lethal force is the option. Here in GA we have a kill the carjacker law. Were you can kill a carjacker and be immune from criminal or civil prosecution. You are also allowed to carry in your car without a license.
The piece of my life that is represented by my material objects that are likely to be stolen, are not worth taking another life over. Although I can also carry a weapon, I choose not to, albeit, I cannot carry one to work.