The pick-ups are, well, picking up

With the understanding that the guitar pick-ups are activated by changes in their magnetic field and the creation of a magnetic field around a flowing electrical current it is not surprising that the guitar pickups create noise (when paired with an amp of course) when adjacent to any operating electrical component. This includes wiring. The catch is that having voltage present alone isn't enough, there needs to be a complete circuit that is operating in order to create a response.