> why don't more developers say "f. you" and walk away from homework assignments, 5-round interviews, cubicle farms instead of offices, etc
Some of us do and some of us don't find it all that terrible. I've declined interviews with homework and told the company I didn't think their interview process was reasonable. Companies are looking for leaders in addition to code monkeys - having a stance on what's reasonable that you can support and explain in a professional manner might lose you a few job opportunities, but it might also win you some respect and serve as a signal that you're mature enough to evaluate the landscape and make judgement calls about what actually is reasonable, which is something managers (people leaders) and architects (technical leaders) do on a day to day basis.
On the other hand, I find whiteboarding to be fairly reasonable for most candidates. I recognize that are a few candidates with social anxiety problems who might only be able to perform ubder an alternate process but in these cases, I think it's reasonable for the candidate to ask and then for the company to accommodate.