[d4mi3n]

You are correct in that handling that volume of physical cash is likely more difficult than I implied, though I don't think removal of cryptocurrency from the equation removes the ability to scale.

In my mind, the catalyzing effect of a cryptocurrency in this context is from:

1. The ability to move something of value digitally

2. The thing of value being resistant to governmental control--crypto can't be easily seized, but a US bank account can.

There may be other properties of crytocurrency that make it useful for ransomware, but I doubt there aren't other vehicles that could be used--though alternatives are likely less lucrative due to the overhead in laundering your ransomeware payment into hard currency.