Gary Myer on the obvious:
Unlike smartphones with independent apps not dependent on content, a TV ecosystem needs to be based on “host” video content. There needs to be an intimate relationship among the content provider, the content distributor, and the consumer device. It’s why cable boxes work perfectly for cable TV; satellite boxes work perfectly for satellite TV; and AppleTV boxes work perfectly with the iTunes store.
Apple will not make a television (but the company could afford to buy the entire television industry).