But Sky was hacked, too....
A few other posters have come close to this, but not touched on it.
Sky cards were comprehensively hacked in the early 90's. Back then one needed a "laptop" PC or an Amiga 1200, attached to the STB via a serial link, and a certain type of dodgy card. I can't remember the exact details as it was nigh on twenty years ago, but I do remember it being done in 1992/93.
To counter this, Sky would every 6-9 months issue a new series Sky card, though until the issue of Series 10 it had little effect. S10 cards however were a game changer, and as I recall proved impossible to crack for sometime, if ever.
So if piracy was to blame, how come widespread piracy didn't affect Sky in such an adverse manner?
And it hasn't gone away. Dreambox is an alternative STB (there are plenty, all based on Linux, such as SpiderBox, OnBox, etc). As an aside, a genuine dreambox 800HD costs £400, a clone costs £150... I digress. Without a subscription, Sky gives, what, 30-40 free-to-air channels. Now plug a Dreambox into the Sky dish, and get about 400 FTA channels.
It gets better - or worse if you are Sky - as a cheap £6/month subscription and an internet connection allows one to watch EVERY encrypted channel on that satellite; on Astra 28.2E thats approx 1400 channels, including every Sky channel. For £6 a month.
A motorised dish kit costs about £45. Mount your dish on that, and there are approx 35,000 channels available (ok, it takes 3 days to tune in!)
Instead of cracking the cards, this is even more insidious; its called card-sharing, and even more problematic for the broadcaster.
So how come piracy didn't take Sky down way back when?