I Don't Understand Kids These Days

This summer, I've noticed what is to me, a disturbing trend: teenagers and twenty-somethings wearing flannel shirts and lightweight jackets when it's 90+ degrees outside.  Surely all of the ones I've seen like this aren't cold-natured.  I don't why but this bothers me.  It makes me think that they don't have common sense to not wear flannel or jackets when it's 92 degrees.  I could see maybe wearing something lightweight if you are outside early early morning when it can get down to the 60's, but not in the heat of the day.  I just don't understand.