Everything has gotten tiny, including the amount of electricity they need to compute.
In fact, the improvements in the electrical efficiency of computing are nothing short of astonishing. More importantly, they are the necessary precondition for the mobile world of computing you know and love. Let me run through a quick thought experiment so you can see why.
Imagine you’ve got a shiny computer that is identical to a Macbook Air, except that it has the energy efficiency of a machine from 20 years ago. That computer would use so much power that you’d get a mere 2.5 seconds of battery life out of the Air’s 50 watt-hour battery instead of the seven hours that the Air actually gets. That is to say, you’d need 10,000 Air batteries to run our hypothetical machine for seven hours. There’s no way you’d fit a beast like that into a slim mailing envelope.
This is a perfect case how to make progresses: either you attack the problem heads on by improving the batteries or you bypass it to work on another side by improving the computer. Both work and the latter is easier in the short run!