I think that there are people who look at it that way but, lets look beyond just power consumption. What happens when a machine produces more heat? You have to get rid of it and most methods of moving heat beyond mere convection tends to make noise and more heat tends to mean more noise (not always but, it's added cost.) For someone who wants a quiet computer, higher power consumption makes that harder and more costly to achieve. For years I only wanted fast and that was that. It could sound like a server for all I cared but, as I've gotten older I've definitely re-evaluated my views on the matter to the point where the next machine I build is going to be factoring in noise because I don't always want to be wearing headphones or cranking up the speakers just to hear what's going on.
So while you've made an excellent point with respect to the cost of power itself, it doesn't factor in the downside of needing beefier cooling to handle it which has side-effects that aren't necessarily measured in financial cost but, there are some that aren't even related to the cost of energy itself.