I’ve always thought it had something to do with absolving themselves if liability.
From what I understand, companies hired by copyright owners send a DMCA request to whichever ISP owns the IP addresses that show up in their honeypots.
ISP has to act on those requests in some way, so they send a sternly worded letter that basically says “we have been notified that your network was used to download copyrighted material illegally. Piracy is bad, you naughty boy/girl. If this continues, we may have to take action which could include canceling your service (don’t worry we won’t because we want your money)”.
Hypothetically, they could turn your information over to the digital rights company, who then could hypothetically file charges against you, but there is established judicial precedent in the US that says that showing that activity came from a specific IP address isn’t enough to convict an individual of a crime without more evidence. Could have been anyone in the household, or it could have been someone who hacked into the network and used it for piracy.
If we want to get even more hypothetical, they could try to convince a judge to issue a search warrant, seize your device, and look for evidence there, which could be used to convict you. But that is an insane amount of effort to go after one of the hundreds of thousands of people who downloaded an episode of game of thrones an Ubuntu ISO.
They do pull out all of those stops going after the original uploaded, though, but if that’s you you’re using way more than a VPN.
