Battery Relocation Question

Ok I was just wondering why.My kill switch will cut the car off when you turn it off.My car kills all the power even the alternator with out all the relays.I never seen any thing happen to a car from a wiring problem even in a crash.The only thing I have seen was wrong and sloppy wiring.Also you will have a welder back there in a crash if metal touches any thing on the relay.I just wanted to know.I am not saying it is a bad thing,just learning.Also wanted to see if it was one of those what if things.Sorry I din,t believe in that.I believe do it it right the first time and you don,t need extra fail safe systems.Also I have been running my wires down the left side inside the cars for 35 years with no problems.I just think that is the persons choice Mark