I should emphasize that I'm not trying to comment on fairness, one way or another.
I'm pointing out that location-agnostic salaries are often trading one segment of the global talent pool for another, since what I've seen in practice is more like "everyone gets paid 80% of a Bay Area salary".
I agree with the other commentator who said: It's not stupid to pay a location-based salary, but please don't pretend it has anything to do with fairness. It's not about being fair - it's about the company trying to save money by getting a discount on employees when that discount is available.