A lot of it is the sheer bureaucracy of chasing down actual pirates and weeding them from people who just happen to be on the same IP address.
If one guy visiting an apartment block downloads a torrent from a public connection, what is ATT supposed to do? Shut down Internet to the entire building?
This is an undue burden for ISPs, even if the content isn't living in a gray zone of legality.
Yeah IP owners really want to have all the benefits of ownership with none of the drawbacks. After lobbying for and receiving a blank check to be able to rent seek indefinitely, they are constantly acting to outsource any cost of detection and enforcement of "their" property. Disgusting how goddamn entitled they are.
I don’t know why you’re being downvoted for this. Even with CGNAT and related technologies, each modem still has a unique MAC address at the cable/DOCSIS level (even without loading Ethernet on top).
Where you could be wrong is buildings with large networks, say an apartment building with wired Ethernet to all the units but all being routed through the same WAN(s), but even still I’d hope that the network is managed in a way that it’s not hard to tell which unit is which IP internally. Unrelated but I’d also pray that each unit is on its own VLAN for security.
There are some apartment buildings with shared Internet connections that are just open and public; It's crappy but cheap if someone can't afford individual connection
Personally I’d die for Ethernet straight into my unit, I had that once in a new building and it was fantastic (though you still had to pay an ISP individually), if only to avoid cable modems and the like. My current cable ISP wouldn’t provision IPv6 to their very own (old, clunky) modem so I had to go out and buy one that doesn’t care whether or not it’s provisioned.