Media companies' subscription revenues are generally more stable than advertising revenues, or revenues from selling one-off items (e.g. newsstand, book and CD sales etc.). There are exceptions, for example even the subscription revenues of financial information providers such as Reuters are cyclical because they are selling to a highly cyclical industry.
Not only are subscription revenues less cyclical, they are also more visible and predictable because customers often need to make a positive decision to discontinue a service rather than a positive decision to buy, which makes them more stable. Subscription services, whether for business or domestic use, also tend to become things that customers are used to having and dislike doing without. Customers do subscribe and unsubscribe so it is important to monitor churn.