I used to think this until i saw the letter from Comcast one day at my clients home.
It literally said to cease and decease illegal downloading and even new what had been downloaded.
If they didn’t, Comcast would stop being their ISP.

Anyway a easy way for Comcast to know where most of the illegal servers are would be to buy a kodi box or twelve and track the ips of those servers and simply bam them.