Because the infrastructure that is needed to both generate and distribute electricity (thus making it "usable") is often partially or fully state funded. I think thats the case even in the United States; while power companies are privately owned, the cost of building new electrical infrastructure is often subsidized by city and/or state governments.
So if I were to buy a few acres in a cheap place in the Southwest (AZ or NM or West TX), install solar panels to generate electricity and set up rest of the machinery (ASICs, internet fiber) to mine bitcoins, you won't have a problem with that?
I think so, proof of work is ideal for the development and cultivation of stranded energy.