eli5: Why does it seem like every civilisation uses coins as currency even before there was a lot of mingling?

Question

I just saw a photo of old coins from like 1 or 2000 years ago and they are all round.
Why is it that they all use coins and not squares or something else completely?

In: Other

Answer 1

Fun fact, that coins and bank notes (cash) only make up a small fraction of the total amount of ‘money’ in the world. About 90% of all money only exists on electronic accounts.