What so they are going to take billions of people to court? Don't be silly no matter how corporate some companies are, someone is going to notice, you only hear of one every now and then and that ends up in the news.
The truth of the matter is millions of people are downloading torrents world wide, I doubt in the UK this would even be entertained in a court of law especially if a corporation obtained information on you illegally, as soon as evidence of that is proven then any case is dismissed from court, R.Kelly got away with accusations of child molestation because the evidenced obtained on him came from questionable legal grounds.(I'm not saying he did anything wrong but I'm also not saying he didn't, just the evidence was thrown out of court)
I'm sure millions of other court battles have ended on the same grounds of illegal evidence, especially where corporations are involved. I think that a lot of the time when it's a civilian being sued they either don't know the law to use it against the companies or they don't have enough money for a high end solicitor who does.