If I'm too cold and my power goes out I have a lot of options to survive. I can put on more clothes, get under a blanket, light my furniture on fire, etc
If I'm too hot and my power goes out, I die. Once the wet bulb temperature gets above a certain level in shade, there's nothing that can be done to stop me from dying except Air Conditioning.
Hint: Phoenix is at 17% humidity today, even their all time high of 122 doesn’t push the wet bulb temp out of the safe range.
Now include climate change raising the temperature and changing the length and severity of monsoon season, continued development raising the heat island effect.
It doesn't matter what the average wet bulb temperature over the entire coty over a long period of time. It matters what the peak wet bulb temperature is for significant number of vulnerable people. The wet bulb temperature only has to get very high once to kill a large swath of people.
I understand just fine the wet bulb temperature has been within safe levels for the vast majority of people so far. My concern is about the future.