I think ransom is also a bit of a misnomer that the hackers deliberately use to frame the transaction in a more positive light.
I mean, it's just extortion. Nothing is being ransomed, you don't get something back and you can't really secure something already lost. It suffers from the same problems as other forms of extortion, namely that you can't really trust the other party to do what you want and really they have no incentive to do so.