Earlier quoted context omitted.
That assumes that all money is of equal value. Which on one level it is, but on another level, the relative purchasing power in different geographic areas is a real thing. Normalising based on that means that in effect you're paying people for the same relative quality of life, rather than same absolute value, which can be very different relatively.
The average global relative purchasing power is already reflected in the currency exchange rates. But generally there is no such thing as a "single" purchasing power. Some local goods may be cheaper in developing countries, but some others can be more expensive. If you don't know exactly what an employee is spending their money on, you can't really tell the purchasing power of their money. A big family with more kids…
I for one would love to be encouraged to move further out to the countryside. That's the long-term plan anyway.