Here is the thing. You want to buy $500 worth of illegal drugs. So what do you do, you would go to your dealer. Now there is a catch. You can use your bank’s phone app to transfer money from your account to your dealer’s account – but how do you explain that if the police investigates you? The same will go for illegal guns, or stolen goods. There will have to be an alternative system for getting income into the dealer’s account without it attracting attention. One could require Amazon gift cards, but this will only be good at Amazon, and you likely can’t buy your drug production methods from Amazon. While it will likely still be possible, it would make performing illegal activity much harder. You could also use crypto currency, but this is dependent on the ability of the crypto currency, and will cause a lot of friction in converting crypto currency to Kaldan Dollars. There is also additional cost in converting currencies which reduces the profits.