People find ways to use the systems that surround them in creative ways. It doesn't matter how roundabout, unintentional or just plain weird the results of these usages are - people will do them anyway. Especially if it gets them something they want.
This, incidentally, answers the question why you really won't find any torrents of Heart of the Swarm around. By feat of unintended and very specific usecases.
It turns out that if you have the Blizzard equivalent of the demo version of Wings of Liberty, downgrade it to a very specific version of the game, block the game from the internet, run it in offline mode and load a savegame from the HotS campaign - it works. All of it. It shouldn't work, and no one at Blizzard intended it to work, but it works. (Don't ask me about the specifics.)
And people use it. Because it works.
Now, you may be reading the description above and thinking - "damn, that's a roundabout way of doing something". Which it is. It also happens to work, and it gives people something they want. The combination of system, work and want is key - especially if there's a lot of people involved. These people soon start to talk to each other, sharing the news that - hey, did you know that if you go through all these hoops in this specific order, it will work?
If you want something, you might give the roundabout way a shot. You never know - it just might work, right?
Which leads us straight back to our opening statement: People find ways to use the systems that surround them in creative ways.
This is, as you might imagine, not limited to people wanting to play computer games for free. It is a general principle regarding people and systems everywhere. Once these loopholes are found, people will talk to each other about them, and before you know it, they become a de facto standard way of doing things.
I wonder what the first person who founded an off-shore company on the Caymans thought. -