Ever run a simple cigarette lighter down across someone's face? It hurts just thinking about it.
A lighter clenched in the bottom of your hand when striking with a hammerfist at neck / face / collarbone / temple give the same force a smaller, harder point of impact = more effective, if you buy into that line of thinking.
A lighter as a sorce of flame is useful for a lot more than smoking. Say you need to start a fire, get a bit of light, defrost a lock, seal synthetic chord, sterilize a needle (non hypodermic), light a gas stove or candle....
This is why I try to have 2-3 spread around my bag, room, or work table at all times.