Cable providers are content distribution, not production....
Yes, there's some overlap -- quite a bit at times, but that's the one thing that seems to be missing in most of this discussion (and about books, too). In the music and book business, there was a complete vacuum in terms of convenient distribution channels. The producers would ship product to a brick and mortar location, and then the consumer would have to get up off his couch and go to the book- or music store. This meant that there was nothing (generally speaking) to supplant when Apple or Amazon got their respective bits rolling. When the comparison is "get up and get moving" vs. "sit on the couch with a snack", it's pretty obvious which choice we Americans will make.
TV (in the US, at least) is a different ecosystem, though -- not only is there an existing choice of convenient delivery mechanisms and providers (local affiliates over-the-air, cable, satellite), but many of those choices are very well entrenched with, and exert quite a bit of power over, the actual content producers. Apple has a (relatively) easy time of it going to a label and saying, "iTunes is the entrenched market -- sign with us or starve" because the labels don't really have an alternate competitive distribution channel. It's a fairly steep hill to climb to go to a content producer (say, Bad Robot) and say the same thing.
Also, keep in mind that it's the established players that front a good deal of the production costs for the content producers, too, and that the cost of producing books (writing, editing, publishing) or music (writing, recording, publishing) are miniscule compared to the cost of producing a quality mass-appeal scripted TV show (by "quality" I mean "production quality", not "artistic quality").
Now, none of this is to say that the existing system is a particularly good system from the consumers' point of view, or that it should be preserved, or that TWC are anything but horrible, or even that Apple or any other tech player can't change the nature of TV, but rather that this is a very different battle for them to fight.