Easy: Because the wires are wrapped in paper, if you simply light a lighter next to them and hold it to the paper for a few seconds, you have kindling. Then, if you can find something in a plane that's not fire-retardant and heat it with the flaming piece of paper enough, voila: an inadvertent fire.
Why go to the complicated step of insulating a wire with the paper? You could make the situation much easier by just tearing some paper out of your notebook for kindling.
Not sure how one would manage to sneak a lighter onboard though.
