If there was a subscription service where you could download say x ammount of songs/movies/TV per month, or you sign up to a TV series and you get the episode soon as its shown on TV, people would pay as they're already paying for download services.
You can buy a series in advance on iTunes, I believe, and watch anything they have on Netflix for a fixed monthly price. These services are far from universal, though.
I've seen these but the cost of them was a bit silly considering I already have sky. The main reason I download the series is so I can watch them in bed on my TV, instead of having to sit in the living room to watch them. The other issue that most of the media companies dont look at is countries where they dont sell the rights to watch a show or they sell the rights to broadcast months after it has all shown in the US (I have a friend in Jordan who loves House but can't get it on any TV over there), so people download it, same goes for movies film comes out in somewhere not in your country for a month. So you download it, as you have no other way to access it.
Music is highly pirated, but I believe its stupidly overpriced anyway. Even buying off Itunes is crazy 80p a song, I read to fill a 120gb Ipod from Itunes would cost about $20,000 (40,000 songs). Media companies have build themselves up giving out massive record deals to artists but the world has moved on and something is only worth what people will pay, most real fans will buy the album, go to the gig etc anyways. If I like a artist I'd rather give them money by going to the gig than giving money to the record label.
Pirating is bad, but really when the alternative is stupidly overpriced and extremely restrictive interms of what you can do with the content once you've paid for it, its far easier and flexible to just illegally download the music!