Cap Fashionistas - Please School Me

I must admit, The Critical Thinker is truly ignorant of why caps are worn in this manner. I need some of you "cap scholars" or "cap fashionistas" to school me on this. I see it daily and just continue to wonder. So if you are a cap wearing specialist out there or can forward this to someone who is, I would love to hear the thought process or reasoning behind the wearing of a cap like those in the photos. I hope the answer has more substance than "It's the style."