As a child, I considered style choices a silly and inconsequential distraction from the beautiful truths of the universe: e^(ipi) + 1 doesn't care what I'm wearing, so neither should I, therefore it doesn't matter, QED.
While today I still wish fashion would just go away so I could wear this conference t-shirt in peace, I contend it offers a reflection of who we are. Consider that while half the Senior Developers of the world can't program their way out of a FizzBuzz test, and half the world can't even read at all, everyone can look at someone's dress and decide if it's fashionable for their demographic. "No, it offers a reflection of what the establishment wants us to be!" I'll leave it to the reader to reconcile those two views. "But I just care about finishing Project Euler problems in APL so I just decide to wear sandals and this old shirt like all my friends!" Fashion mattering doesn't depend on you caring. Even you, APL-man, know Zuck couldn't wear his hoodie working for Quinn Emanuel unless he owned it (real question: how many people show up in suits at facebook?).
I was shopping for pretty scarves (!) with a product designer and suggested that ads are the clearest reflection of what a given demographic is. He agreed so quickly I wondered if I were late to the party. So when the Scientology ad in the Atlantic showed up, I thought of my favorite TLP quotation: if you're reading it, it's for you. The obvious question was "why is the Atlantic publishing this!?" The more depressing question is "why am I in Scientology's target demo?"
Fashion is an advertisement about yourself. "But the relationship is not always so obvious!" Hence the hoodie the world's richest web geek refuses to remove. "But I don't care what Zuckerberg wears!" If you're reading it, it's for you.