There are two reasons why mice find wiring so irresistible, the first one being that they simply enjoy chewing things and the second – that the toughness of wires and their casings present mice with the perfect tooth sharpener.
Mice have very strong, sharp teeth which are constantly growing, so they need to chew on whatever they can find to control the length of their teeth. Chewing on tough objects also has the bonus of strengthening and sharpening their teeth, so that they can chew through things even faster.