The ransom is usually quite small (i.e. <1k), so it might be considered a 'cheap' lesson to learn that you should keep your software up-to-date and secure your network. (With the exception of 0-days, but you can't blame anyone falling victim to that)

My point is, the ransomware is just 'prove' that your computer is insecure. If criminals can encrypt your files, they can also steal it (i.e. upload it somewhere). So in some sense, the ransomware creators expose vulnerabilities that would have otherwise gone unnoticed.