That's because a great way to make electricity happen is to spin magnets inside a coil of wire. The turbines spin large magnets inside coils of copper wire. That's what a generator is. The spinning magnet sort of brushes electrons along from one copper atom to the next copper atom. The energy of that movement is the electricity that flows through all the wires looped together with the generator's coil of wire.
Electricity flows in a loop.
In the comic next week we're going to see how eletrical energy flowing in a loop is turned into light. Then the week after that we'll make lightning with stuff from around your house.