Because not everyone lives in the UK? And even if you do, ISPs can store data long-term, waiting for the laws to change and then retroactively find which custom

Because not everyone lives in the UK? And even if you do, ISPs can store data long-term, waiting for the laws to change and then retroactively find which customers they should keep a closer eye on. Not to mention the non-ISP groups which also monitors the DHT for who downloads content they "own", ready to serve the data to governments at request.