From Game of Thrones: How HBO and Showtime make money despite low ratings:

On the networks and basic cable, shows are a delivery vehicle for advertising””and if a program doesn’t attract a big enough audience for those ads, the consequences are clear: It’s pulled from the schedule, and a new show is dropped into the time slot. On those channels, viewer is just another word for person who sees a commercial.

This is contrasted with the subscription model that premium channels like HBO and Showtime use:

The premium networks are in the business of selling subscriptions. A Showtime spokeswoman told me that the channel’s goal is to satisfy subscribers and to entice non-subscribers to sign up. They keep their customers happy by allowing them to watch original TV series, exclusive movies, and sports programming whenever they want to.

I’m pretty sure you know where I’m going with this, but the situation is analogous to what we see in online publishing today. Ad-supported sites aim to rack up all the “eyeballs” in the world so that they can be resold to advertisers. Subscription-based sites aim to satisfy their readers by providing great content that will, in turn, entice more non-subscribers to sign up.