> As someone coming from the hiring side, I don't understand how these companies are finding enough candidates that they can afford to put up all these arbitrary requirements.

Well, they're not; that's one reason why there are so many stories of "not enough qualified developers".

If I give in to my conspiratorial side, I'd say having these arbitrary requirements is entirely intentional, so a company can either: a. not have to hire anyone at all b. lobby for H1B or c. resort to offshoring, outsourcing, etc.