In other words, the use of standard measures that were portable and external to a society's local norms tracked closely the diffusion of settled agricultural civilisations and specialist societies. This is unsurprising.
In the absence of trade there would be no reason for them to stabilise, but with trade there is every incentive for them to do so even over long distances and between people groups who don't know of each others existence.
That force is commerce, and it has almost never been absent in human history.