As someone who's run two remote companies now, I have struggled with this dilemma as an employer. Because I agree with you, if a person is worth $x to the company, their location doesn't change that.
The flip side, though, is that I also want people to be on relatively equal footing. Not everyone can move to optimize their relative adjusted income, and the problem with a salary number is that it doesn't reflect status. An entry level SF salary will get you a house + a lake house in Oklahoma. A person who owns a vacation home is living an entirely different life than someone with a roommate in Oakland.
If you _don't_ adjust salaries for cost of living it makes that even worse, because suddenly you're probably paying less than someone in SF or NYC needs, more than what most people need in other states, and paying a crazy high localized salary to someone in Vietnam.
All that said, we're doing the same salaries regardless of location. And I'm still not sure that's the right choice.