You're asking the wrong question. Why do modern computers burn so much energy? 12 years ago, I was using an Amiga600 which came with a 15 Watt power supply. Nowadays, try finding a laptop that has a power supply less than 100 Watts. Furthermore, you can buy gamer tower cases which come with 1000 Watt power supplies. WTF?
Obviously power consumption has gone up because demand for performance has outstripped increasing power efficiency. But the Forrest Curve is catching up, as we can see from all the enthusiasm for sub-$400 computers.
(BTW, laptop power supplies are double-sized, since they need to be able to power the laptop and charge the battery simultaneously. e.g. a 40W laptop will have an ~80W supply.)
