There is 1 main cause of movie piracy: the movie industry. Just like the music industry they failed to give the public what they wanted; ie. a usable on-demand digital service for a reasonable price. No sympathy for them in the slightest I'm afraid.
However..... arsing around with Torrents and Usenet is just a pain. Especially if you're over the age of 20 and prefer to kick back on the sofa with a bottle of wine and just watch a movie on your TV without buggering around encoding, burning etc.
Sky goes a very small way to address this. It's great if they happen to be showing what you want, but useless otherwise. I binned my Sky subscription because there was simply never anything I wanted to watch. Plus I refuse to watch any TV channel with adverts.
An Apple TV is one possible solution. A little set-top box which allows you to download an watch on-demand movies, and has a pretty large choice.