To elaborate, intellectual property law is essentially "use it or lose it" - a company that does not defend its IP against unauthorized use is likely to have it invalidated. One that actively promotes unauthorized use is almost certain to.
If HBO is not making a good-faith effort to secure for George R.R. Martin all the royalties that he is entitled to (which deliberately leaking GoT to torrent sites certainly would not be), then there isn't a court in the world that wouldn't consider HBO to be in breach of contract and return the TV rights to Martin.
> which deliberately leaking GoT to torrent sites certainly would not be
This is my central question that has not been answered. How is deliberately leaking GoT not beneficial to HBO? How does the company generate revenue from everyone watching it on their service at once (remember, HBO themselves mentioned that they don't mind piracy and the old joke is that for every one subscriber to HBO GO there are dozens of other, non-related people using those credentials)