I have to simplify to to a children's book to fit into a comment. The full picture of the complexity fills many many books. There are many different cultures i

I have to simplify to to a children's book to fit into a comment. The full picture of the complexity fills many many books. There are many different cultures in history with many different levels of monetization. However for 95-99% of the per-indstrial population you are a peasant farmer. You don't need money because you can grow everything you need. (this doesn't mean you do, only that you can) For the other 1-5% though things are different. The closer you get to 5% the more money everybody (including the peasants!) needs to support your way of life. At 1% you only have peasants and a few "big men". At 5% there are a lot of non-nobility who the farmers are supporting anyway. That is only possible if the farms specialize into whatever grows best for them. In turn that means the farmers need to import the other food items they might want meaning they need money to buy it. The farmers also need to trust that if they have a crop failure they will still be able to eat. As soon as farmers don't trust they will be able to eat even in case of crop failure they will diversify - the farm will produce less food overall, but no one crop failure will make them starve to death! Either works fine for the farmer but all those city folks starve to death in the second case since the farmer is self sufficient on much less food production than it could produce.