It’s common for single coil pickups to pick up 60 cycle hum if they are near any outside electrical interference such as computer monitors, output transformers, lights, motors and many other things that cause 60 cycle hum. 60 cycle hum is common with single coils pickups. Remember that when Fender was making instruments back in the 50’s and 60’s, many of the amplifiers used had small output and power transformers for an average 10-45 watt amplifier. As the amps started getting bigger so did the output and power transformers thus causing a larger area where the stray electrical interference could be picked up by the single coil pickups. As hotter single coil pickups started hitting the market, so did the 60 cycle hum get louder through the amplifiers.