It is true, that we use torrents in order to download pirated content (yes, you can get legal stuff as well, but closed trackers are largely about getting the stuff illegally).
Unfortunately, current fight with trackers show, that no tracker is safe.
Just in the past few months we've lost several best music trackers. We've also lost Black Cats games.
So i personally prefer to maintain good ratio on several trackers, just in case one goes down.
Now, at the end of the year i have some time to look for extra invites, build-up the ratio, etc.
But when i'm travelling, i just don't have time for that. I need an opportunity to get what i want and to get it quick. In some cases i don't even have the opportunity to seed the stuff i've downloaded (and takes ages for some old movies for get ratio of 1.0) So i have a good buffer, i can get what i want anytime i want, without hurting the community.