Hypothetically, because they've reached a local maxima. And they recognize that their customers like their current product.

As the article itself notes, few people buy a subscription service for one or two shows.

If Netflix can continue to bid high enough to starve its competitors of high-quality content (because it can amortize its costs over a larger subscriber base), then no competitor can grow large enough to compete without running substantial initial deficits (which Netflix can make temporarily worse if they choose to, by overpaying for content and driving prices up).

So essentially, lack of competition.