I think a major problem with people in general is the inability to think ahead a little, and anticipate.
So the footwearers you mention take no account of the temperature, or the under-foot conditions, but that's just how people go on. Similarly, you see or hear a weather forecast which predicts rain, so you have a coat and / or an umbrella, and see loads of people with neither - simple anticipation, not thought about in advance.
I am seriously lucky, I have only ever had bad feet once - after my first trip to Glastonbury when I neglected to wear socks thick enough to protect my feet from being rubbed by my brand new wellies - blisters for three weeks was my reminder, but i thought about it the following year!