Earlier quoted context omitted.
Because they are power-hungry and everyone knows that. More generally because the climate in central Europe is not like Arizona, Utah, New Mexico, California but hospitable during the summer season without AC. AC makes it more comfortable during hot days but it is still doable without. This is only true for private households. Since 10 years ACs are widely used in a business environment.
Except, modern AC is pretty efficient. I have a decent monoblock cooler in our apartment in Berlin. I also have a 1-second sampling power meter. The AC unit uses about 700 watts when active cooling, but of course it cycles so that's not all the time. We also only run it when it's 30+ during the daytime. Overall, it's only added about 15-20kWh to our monthly usage. (2-person household, about 200kWh/month average)
> What on earth are people spending electricity on?
It's exactly that. An AC, probably one additional appliance among others, adds another 10% to the total and somehow we manage to frame this as efficient and thus the right thing to do.