But they don't use that either in the context of real-world electricity usage. Maybe in the middle school classroom setting, when you can make up the numbers you work with, but when I'm trying to quantify how much energy something uses at home I multiply how many watts it uses by now many hours it's running. Divide that by 1000 for kilowatt-hours, and multiply by $.11 to know the cost to do it at home. If I need to do a multiplication/division of 3.6 million when nobody else is, something's not right.

Similarly, a meter is a standard unit for length, but we don't use it when measuring the distance to different galaxies because light-years are more practical at that scale. If you start using meters you'd get some funny looks, just as I'm feeling for joules instead of kilowatt-hours. But you know, "almost a kilowatt-hour" makes for a pretty boring headline.