Because that's not how copyright law works in the US and some other jurisdictions. It's not based on common sense but what the rightsholders were able to enshrine into law in societies that favor corporate rights over personal rights.

Things can be ethical but still illegal, like in this case. Realistically they're not going to do much more than send you a notice via your ISP (if you don't use a foreign seedbox), but it's still illegal.