Nobody wonders why. The Bay Area is clearly more expensive than anywhere else other than NYC. Nobody has ever argued that that isn't true. The salaries are also significantly higher, to compensate.

What is being argued here is whether you can live comfortably on a six figure net salary (after taxes).

That housing is expensive in the bay area does suck, no doubt, and is super annoying. But it's far worse for non-engineers. Engineers are fine, and frankly, are the ones who are driving the prices up, by virtue of being capable of and willing to pay more, as companies continue to increase compensation.