In the industry of broadcast media (incl. air/cable/satellite), you don't drag broadcasters, broadcasters drag you. They are the big dogs with the market majorities and the money to call the shots.
Why do you think Directv can shore up all rights to the NFL market? That's some of the most expensive (if not the most expensive) content available. A streaming app on internet boxes couldn't even provide 10% of that revenue, yet undermine the entire existing market. And for what, so a minority of consumers can enjoy their internet streaming experience at the expense of the majority of broadcast costumers. It goes for all content providers; no reason to give up the goose that lays the golden eggs for a lone golden egg that may hatch in the future.
The amount of exposure available to streaming boxes is still very minuscule compared to the gargantuan markets held by broadcasters. Why would they jeopardize their multi-billion dollar markets they currently enjoy, for a multi-million dollar market that "should" grow, eventually, over time.
As for Apple they provide the services on the Apple TV that content providers agree to. If there's no streaming subscription services yet, it's because no content providers are willing to agree to it yet. No content, no appeal, no service.