Great content alone won't maximize stickiness - better UX than competitors is also a major selling point. For example, on Netflix you currently don't get ads, which when compared to broadcast TV or even some streaming services, you have to suffer through (seeing ads on YouTube even while paying for a subscription is an example of user hostility).
Competitors don't sit still either - they're busy trying to put together a package of good content and improved UX as well in order to better compete with Netflix. Incumbents generally are harder to unseat though, whether it be in politics or in business, the bar that needs to be passed is "Why should I move from/pay for X?" - in this case, Netflix wants to be the X.