It really isn't. I have a pocket-sized device that would utterly thrash a supercomputer from a couple of decades ago, and it goes a day or two on a 20Wh battery. Going full blast it'll consume maybe 25-30W, which is less than the idle power consumption of far less powerful devices from not all that long ago.

Incidentally, cars are also a lot more fuel efficient these days than they used to be.