I've heard it mentioned various times that a fiat currency's value in any organized society comes from its ability to pay off the controlling state (i.e. taxes).
Whether it is dollars to the IRS, colored beads to the local chieftains, or copper coins to the Lord of the manor, it doesn't make a difference. The ability to 'pay off' the state in power, with legal permission and ability to use violence, gives that currency value.
I think you're right in this case. The ransomware authors functioning similarly to the state. If i couldn't access my computer I would have to buy bitcoins with my other assets.
Whether it is dollars to the IRS, colored beads to the local chieftains, or copper coins to the Lord of the manor, it doesn't make a difference. The ability to 'pay off' the state in power, with legal permission and ability to use violence, gives that currency value.