Maybe there's an /r/numismatics that would be better for this question, I have a tough time believing that people who worked the land/tended the flocks were immediately won over immediately by precious metals - seeing as how fearful of change people can be.
The appeal of coins was that they were standardized versions of what was already being used. People have been using precious metal for barter for pretty much all of history. When coins came out, already stamped with the weight and purity they were easier to do transactions with.