Fans of HBO's unique selection of premium content will be thrilled to learn that the channel's mobile app, HBO GO, will now be available to even more subscribers. Well, they'll be thrilled as long as they already subscribe to HBO via their cable or satellite provider.

Customers of Time Warner Cable and Cablevision will soon join most other cable subscribers in being able to view HBO's massive library of original content from their smartphones and tablets. So far, the response among those subscribers to the year-old HBO Go app has been rather positive. For many of those who don't pay for a cable subscription, the response has been, "Hey, can I get your HBO Go login info?"

That's because as beloved as HBO Go is, the service is not available to anyone who doesn't have a cable subscription. That's not just a feature of the early beta period of this experiment, either. It's likely to remain that way indefinitely, if you accept the word of HBO Co-President Eric Kessler.

Historically, the only way to get access to HBO has been to pile it on top of one's existing cable bill. The cost of those subscriptions have been going up and turning off more and more consumers, who are increasingly able to turn to online sources like Hulu and Netflix for video content. The so-called cord-cutting phenomenon was dismissed by Kessler, who said it would cease to be a significant force once the economy turns back around.

That may sound like a risky bet to some, akin to print publishers crossing their fingers for an economic revival to somehow bring their old revenue streams back. Yet HBO has important, deeply-rooted relationships with cable providers to preserve, so this stance isn't shocking.

Unlike many of the other channels available on cable, HBO is known for a wide selection of premium, sought-after content. Because of the way cable billing typically works, consumers don't have the option of picking and choosing channels they want and leaving out the rest. It's all or nothing, and if you want the really good stuff (like HBO), you've got to pay extra.

The Web would seem to open up the possibility of a new approach, allowing people to pay a monthly fee for only the premium content they want, and many have indicated that they would do so for HBO Go.

So far, the business relationships of the legacy players have proven too entrenched to budge, even in the face of growing demand. Although it's on the rise, cord-cutting is not yet a big enough trend to pose a serious threat to cable, to which millions of customers still happily subscribe. If people don't stop ditching their cable bill, perhaps HBO will reconsider its position.