Or they'll just use any free proxy/VPN. TPB nowadays just serves magnet hashes, even the slowest, more restricted link is enough. The rest goes through DHT.
In my experience, most of the people who are serious about torrenting don't use The Pirate Bay anyway and have long since moved to members only trackers (like Demonoid etc).
I personally have had really bad luck with private, members only tracker sites. If I don't get on the torrent within minutes of posting, I can't reach the desired 100% seeding goal. On the other hand, this is ridiculously easy to do with public tracker sites (such as TPB).
There is huge variability in private trackers, some are awful (Demono's adds have become unbearable), some are pretty good, like karagarga, which has lots of films I simply could not find anywhere else, legally or otherwise, and others are awesome, like what.cd.
This is the case with the best and most serious private trackers. If you're serious about keeping a good ratio, just get a seedbox and set up a script to download the torrents you want as soon as they're posted (most trackers have an IRC bot that announces new torrents).
What's the purpose of torrent again? Is that the thing people use to steal copyrighted works or are millions of people using it to exchange wedding videos? Torrents are the reason movies and music is so expensive relative to their actual production and distribution costs.
The purpose of BitTorrent is peer-to-peer file sharing. Period. While it is all too often used for distributing works illegally, its primary purpose is not that. Consider reading the Wikipedia page[1] for some examples of effective and legitimate uses of the protocol.
