one current only that mean you only depend on central bank of that money so that when loose it you will loose any thing it is so risky so that make more than one income soruce
I agree. If you have 1 currency in the whole world. It would be easier to buy things of course. But would take a huge risk with it. Because if there is a central bank for it and it will get hacked or something. So many people will lose their money.