Encryption is difficult to get right. Multiple ransomwares have failed because they screwed it up and it was possible to decrypt without paying. It's also time

Encryption is difficult to get right. Multiple ransomwares have failed because they screwed it up and it was possible to decrypt without paying. It's also time consuming. It takes a long time to encrypt every file on a hard drive and antivirus will scan for that kind of behavior. Whereas throwing together a program that corrupts every file on the hard drive is not too difficult.