Defensive knives on the center line

I see people on the internet, oftentimes instructors (thinking of someone like James Yeager, although he's not the only one) wearing a defensive knife on the center line of their body. Usually they are appendix carrying as well so the knife is right next to the gun.What is the thought process here? My understanding is that, since both are deadly weapons, the knife is for when you can't get to your gun. The first situation that comes to mind is if you get tackled or knocked down and someone's on top of you. But if your knife is right next to your gun, if you can't get one, you can't get the other.Doesn't it make more sense to have a knife on the weak side, where a reload would be, and the gun either at appendix or on the strong side? What am I missing here? via /r/CCW http://ift.tt/2p5IKPG