The presumption absolutely no one will trade you crypto in your own country and you can't just mail out or in cash somehow seems like a pretty steep one (particularly in Argentina where black market trade of USD and all array of other stuff is rampant); but you must surely see the different between having your cash stored in a private wallet vs a bank account with a country that quite likely has tax and other legal treaties with your own.

I can't imagine it would be a warm feeling for someone with tax liabilities in Argentina to have a white-market bank account in a friendly country nearby.