I don't think i can give an intelligent explanation, cause I don't think there is one.  In has to do in part with not wanting to be tied to closely with the outside word.  Although they don't mind being dependent on the rest of the world for diesel, propane and coal deliveries.  Also, they use DC power.  Most have alternators on thier diesels that are charging all manor of batteries while the diesel is running. 

I will say this, the guy with the windmill uses air motors to run a machine shop that you would  not believe.  He does incredible work.