I think you prove my point (and it's not a bad thing!)
Sociology is interesting. A suit is traditionally a sign of "I invest in my clothes and therefore I have self-pride." (It's also a sign that you don't have to do hard/dirty labor.) It seems culturally America has decided that this is out-dated and are choosing to focus less on clothes as a sign of pride. This doesn't the pride isn't there, just that the ways of showing and seeing it have changed for some or most.
Some people will always think a tee-shirt or shorts look worse than a button-up and pants. It's a personal sentiment for sure.
Over the decades, a suit has morphed from "I have power" to "I conform to the norm (and therefore I don't have power)" and with that change it is also apparent why people would want to not wear suits in an environment that traditionally required them.
Location may factor in here. They may look nice in NYC but they probably wish they could wear whatever they wanted (Zuckerberg) in Southern California.
Only lawyers and bankers dress fancy everyday here. And not even all bankers.
I've avoided these kinds of careers because I want to be graded on my skill, not my ability to dress well. And suits are uncomfortable, and I like to be comfortable.
It's not that I cannot afford to wear suits. Its that I dont like suits. Add in the marginal cost difference and I'd rather wear a tshirt. It's the market punishing the inefficiency of requiring your workers (or date) to dress in a certain manner when it adds no true value.