For Netflix, it's not just about new shows driving subscriber count. I'm probably summarizing incorrectly, but it also has to do with their royalty structure. Canceling a show after two seasons allows them to save a ton of money by short-changing their creators and stars, while still getting headlines about signing huge-figure deals with those same people.

[source]: https://www.hollywoodreporter.com/news/general-news/tvs-new-...