I've said this elsewhere but there's a kind of old world wisdom which dictates that heat is necessary for survival but staying cool is simply a kind of decadence. One of those beliefs that hasn't updated with the Modern Age and certainly not the past several Summers.
It's because the people who can't up with that "old world wisdom" lives in damp, cool climates that didn't see truly dangerous heat until this century. If you ask anyone from the Middle East, Northern Africa, Central America, or the Outback, they world probably disagree and tell you why.
I think this is it though - it is genuinely only in the last 3 or 4 years that we have needed to consider AC in the UK, so it does still feel like a luxury to many here