When Apple's video streaming service made its debut on Friday, it came with two billion U.S. dollar worth of original programming -- a feature widely considered to be the most powerful magnet for new subscribers.

But for Apple TV+ and its rivals, whose monthly subscriptions are cheaper than traditional cable packages, keeping viewers is a huge challenge.

Streaming providers like Netflix, Apple TV+, Walt Disney Co's Disney+ and AT&T's HBO Max tout flexibility: sign up to watch a new show, cancel when you want.

Besides spending millions of dollars on library content, media companies are using programming, promotions and other strategies to avoid cancellations, or "churn" in industry parlance, and retain subscribers who are costly to acquire and easy to lose.

"Churning off of a service once meant finding the phone number of your cable operator, navigating an automated menu and waiting on hold," said Rich Greenfield, an analyst at LightShed Partners. "We now live in a world where with a couple of clicks of your finger on your phone, all of the friction from cancellation is gone."

Disney is the only streaming provider that has used a multi-year promotion to lock in subscribers. In August, the company offered new and existing members of its D23 fan club an annual rate of 47 U.S. dollars for a three-year commitment to Disney+, which is 33 percent off the standard price.

Disney has the advantage of making content for children, who watch the same movies and TV shows again and again. Netflix, HBO Max and Apple TV+ have invested in kids' content to keep subscribers from canceling while they wait for the next original, adult-focused show.

In May Netflix made a rare acquisition of the children's media brand StoryBots for an undisclosed sum. In July it announced seven new series targeting preschoolers.