Interesting. You can test a battery's capacity, too, so I don't think that's exactly it. I also don't think the collective desire for faster CPUs is all that strong; look at how few people bother going to the lengths of, say, overclocking and watercooling, let alone more exotic approaches.
Maybe it's better expressed as a balance between desire and experience. We have a lot of experience with CPUs, and we've grown accustomed to their speed, so our collective desire is modest. But collective desire for better batteries is very strong, and our experience with them is modest. So it's much easier for somebody to say, "Miracle tech! Give me millions!" And somebody will.
