[Workaccount2]

It simply takes a non-zero amount of energy to turn a transistor on and off.

Add up trillions of transistors, flicking on and off billions of times a second, and you get enormous power draws.

What is actually drawing power is the gate capacitance of the transistors. If the transistor were a physical switch, the gate capacitance is the "weight" that must be put on the switch to flip it. Of course this weight gets smaller as the switches shrink and as the tech improves, but it will always be non-zero.

None of this accounts for resistive losses either, which is just the cost of doing business for a CPU.