In some places, it is illegal for anyone other than the utility to resell electricity. MT just changed their laws in this regard. Tesla superchargers used to charge a time based fee that would be higher for times in the charging cycle that took more juice and would taper off as the demand went down. The end result was the close to the same but since they weren't directly charging by the Kwh, according to the bureaucrats they weren't really reselling electricity. Law recently changed so now I pay by the Kwh. Some Tesla AC chargers do have metering features, so in places where it's legal, I expect those chargers to start popping up.