In which case you're multiplying by large numbers so it doesn't matter if you start with Joules or kilowatt-hours, so you should start with the SI unit.

Ok even if that is true and they're both equally unintuitive you're the one who wants everyone to switch to an unfamiliar unit for no apparent reason.

The reason is that there is an SI unit for energy, and using the non-standard unit is dumb.

Why does it make so much more sense to talk about solar and electric car charging on the scale seconds of power than hours that everyone should change units?

Because there's an SI unit for energy, and there's nothing superior about kWh, it just adds to the confusion to have multiple different units that all measure the same thing. You get the stupid situation that Americans have with other units where there's teaspoons, tablespoons, cups, gallons, ounces, etc. all for measuring volume instead of just using L for everything.